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2021-01-23 | Oscillation time and damping coefficients in a nonlinear pendulum | We establish a relationship between the normalized damping coefficients and
the time that takes a nonlinear pendulum to complete one oscillation starting
from an initial position with vanishing velocity. We establish some conditions
on the nonlinear restitution force so that this oscillation time does not
depend monoto... | 2101.09400v2 |
2024-03-26 | On a class of nonautonomous quasilinear systems with general time-gradually-degenerate damping | In this paper, we study two systems with a time-variable coefficient and
general time-gradually-degenerate damping. More explicitly, we construct the
Riemann solutions to the time-variable coefficient Zeldovich approximation and
time-variable coefficient pressureless gas systems both with general
time-gradually-degener... | 2403.17732v1 |
2013-11-14 | The dimension of the leafwise reduced cohomology | Geometric conditions are given so that the leafwise reduced cohomology is of
infinite dimension, specially for foliations with dense leaves on closed
manifolds. The main new definition involved is the intersection number of
subfoliations with "appropriate coefficients". The leafwise reduced cohomology
is also described... | 1311.3518v1 |
2002-12-05 | Dynamic stiffness of spin valves | The dynamics of the magnetic order parameters of
ferromagnet/normal-metal/ferromagnet spin valves and isolated ferromagnets may
be very different. We investigate the role of the nonequilibrium spin-current
exchange between the ferromagnets in the magnetization precession and
switching. We find a (low-temperature) criti... | 0212130v2 |
2005-01-13 | Magnetization noise in magnetoelectronic nanostructures | By scattering theory we show that spin current noise in normal electric
conductors in contact with nanoscale ferromagnets increases the magnetization
noise by means of a fluctuating spin-transfer torque. Johnson-Nyquist noise in
the spin current is related to the increased Gilbert damping due to spin
pumping, in accord... | 0501318v1 |
2005-01-27 | Current-induced macrospin vs spin-wave excitations in spin valves | The mode dependence of current-induced magnetic excitations in spin valves is
studied theoretically. The torque exerted on the magnetization by transverse
spin currents as well as the Gilbert damping constant are found to depend
strongly on the wave length of the excitation (spin wave). Analytic expressions
are present... | 0501672v3 |
2006-05-08 | Microscopic Calculation of Spin Torques in Disordered Ferromagnets | Effects of conduction electrons on magnetization dynamics, represented by
spin torques, are calculated microscopically in the first order in spatial
gradient and time derivative of magnetization. Special attention is paid to the
so-called $\beta$-term and the Gilbert damping, $\alpha$, in the presence of
electrons' spi... | 0605186v1 |
2006-11-27 | Microscopic Calculation of Spin Torques and Forces | Spin torques, that is, effects of conduction electrons on magnetization
dynamics, are calculated microscopically in the first order in spatial gradient
and time derivative of magnetization. Special attention is paid to the
so-called \beta-term and the Gilbert damping, \alpha, in the presence of
electrons' spin-relaxati... | 0611669v1 |
2007-10-15 | Ferromagnetic resonance study of polycrystalline Fe_{1-x}V_x alloy thin films | Ferromagnetic resonance has been used to study the magnetic properties and
magnetization dynamics of polycrystalline Fe$_{1-x}$V$_{x}$ alloy films with
$0\leq x < 0.7$. Films were produced by co-sputtering from separate Fe and V
targets, leading to a composition gradient across a Si substrate. FMR studies
were conducte... | 0710.2826v2 |
2008-10-25 | The domain wall spin torque-meter | We report the direct measurement of the non-adiabatic component of the
spin-torque in domain walls. Our method is independent of both the pinning of
the domain wall in the wire as well as of the Gilbert damping parameter. We
demonstrate that the ratio between the non-adiabatic and the adiabatic
components can be as hig... | 0810.4633v1 |
2008-12-03 | Observation of ferromagnetic resonance in strontium ruthenate (SrRuO3) | We report the observation of ferromagnetic resonance (FMR) in SrRuO3 using
the time-resolved magneto-optical Kerr effect. The FMR oscillations in the
time-domain appear in response to a sudden, optically induced change in the
direction of easy-axis anistropy. The high FMR frequency, 250 GHz, and large
Gilbert damping p... | 0812.0832v1 |
2011-02-26 | Dynamics of Skyrmion Crystals in Metallic Thin Films | We study the collective dynamics of the Skyrmion crystal (SkX) in thin films
of ferromagnetic metals resulting from the nontrivial Skyrmion topology. We
show that the current-driven motion of the crystal reduces the topological Hall
effect and the Skyrmion trajectories bend away from the direction of the
electric curre... | 1102.5384v2 |
2011-04-15 | Lagrangian approach and dissipative magnetic systems | A Lagrangian is introduced which includes the coupling between magnetic
moments $\mathbf{m}$ and the degrees of freedom $\boldsymbol{\sigma}$ of a
reservoir. In case the system-reservoir coupling breaks the time reversal
symmetry the magnetic moments perform a damped precession around an effective
field which is self-o... | 1104.3002v1 |
2011-07-04 | Minimization of the Switching Time of a Synthetic Free Layer in Thermally Assisted Spin Torque Switching | We theoretically studied the thermally assisted spin torque switching of a
synthetic free layer and showed that the switching time is minimized if the
condition H_J=|H_s|/(2 alpha) is satisfied, where H_J, H_s and alpha are the
coupling field of two ferromagnetic layers, the amplitude of the spin torque,
and the Gilber... | 1107.0753v2 |
2012-09-14 | Skyrmion Dynamics in Multiferroic Insulator | Recent discovery of Skyrmion crystal phase in insulating multiferroic
compound Cu$_2$OSeO$_3$ calls for new ways and ideas to manipulate the
Skyrmions in the absence of spin transfer torque from the conduction electrons.
It is shown here that the position-dependent electric field, pointed along the
direction of the ave... | 1209.3120v1 |
2013-03-12 | Thermally excited spin waves in a nano-structure: thermal gradient vs. constant temperature | Using micromagnetic simulations, we have investigated spin dynamics in a
nanostructure in the presence of thermal fluctuations. In particular, we have
studied the effects of a uniform temperature and of a uniform thermal gradient.
In both cases, the stochastic field leads to an increase of the precession
angle of the m... | 1303.2895v1 |
2013-07-29 | Theoretical Study of Spin-Torque Oscillator with Perpendicularly Magnetized Free Layer | The magnetization dynamics of spin torque oscillator (STO) consisting of a
perpendicularly magnetized free layer and an in-plane magnetized pinned layer
was studied by solving the Landau-Lifshitz-Gilbert equation. We derived the
analytical formula of the relation between the current and the oscillation
frequency of the... | 1307.7427v1 |
2014-06-10 | Influence of Ta insertions on the magnetic properties of MgO/CoFeB/MgO films probed by ferromagnetic resonance | We show by vector network analyzer ferromagnetic resonance measurements that
low Gilbert damping {\alpha} down to 0.006 can be achieved in perpendicularly
magnetized MgO/CoFeB/MgO thin films with ultra-thin insertions of Ta in the
CoFeB layer. While increasing the number of Ta insertions allows thicker CoFeB
layers to ... | 1406.2491v2 |
2014-09-24 | Dissipationless Multiferroic Magnonics | We propose that the magnetoelectric effect in multiferroic insulators with
coplanar antiferromagnetic spiral order, such as BiFeO$_{3}$, enables
electrically controlled dissipationless magnonics. Applying an oscillating
electric field in these materials with frequency as low as household frequency
can activate Goldston... | 1409.6900v2 |
2015-02-09 | Large amplitude oscillation of magnetization in spin-torque oscillator stabilized by field-like torque | Oscillation frequency of spin torque oscillator with a perpendicularly
magnetized free layer and an in-plane magnetized pinned layer is theoretically
investigated by taking into account the field-like torque. It is shown that the
field-like torque plays an important role in finding the balance between the
energy suppli... | 1502.02699v1 |
2015-07-24 | Boosting Domain Wall Propagation by Notches | We report a counter-intuitive finding that notches in an otherwise
homogeneous magnetic nanowire can boost current-induced domain wall (DW)
propagation. DW motion in notch-modulated wires can be classified into three
phases: 1) A DW is pinned around a notch when the current density is below the
depinning current densit... | 1507.06748v1 |
2016-01-23 | Nonlinear magnetization dynamics of antiferromagnetic spin resonance induced by intense terahertz magnetic field | We report on the nonlinear magnetization dynamics of a HoFeO3 crystal induced
by a strong terahertz magnetic field resonantly enhanced with a split ring
resonator and measured with magneto-optical Kerr effect microscopy. The
terahertz magnetic field induces a large change (~40%) in the spontaneous
magnetization. The fr... | 1601.06213v1 |
2017-08-11 | Gradient expansion formalism for generic spin torques | We propose a new quantum-mechanical formalism to calculate spin torques based
on the gradient expansion, which naturally involves spacetime gradients of the
magnetization and electromagnetic fields. We have no assumption in the
small-amplitude formalism or no difficulty in the SU($2$) gauge transformation
formalism. As... | 1708.03424v1 |
2019-06-03 | Magnon-phonon interactions in magnetic insulators | We address the theory of magnon-phonon interactions and compute the
corresponding quasi-particle and transport lifetimes in magnetic insulators
with focus on yttrium iron garnet at intermediate temperatures from anisotropy-
and exchange-mediated magnon-phonon interactions, the latter being derived from
the volume depen... | 1906.01042v1 |
2019-09-17 | Microwave induced tunable subharmonic steps in superconductor-ferromagnet-superconductor Josephson junction | We investigate the coupling between ferromagnet and superconducting phase
dynamics in superconductor-ferromagnet-superconductor Josephson junction. The
current-voltage characteristics of the junction demonstrate a pattern of
subharmonic current steps which forms a devil's staircase structure. We show
that a width of th... | 1909.08004v1 |
2019-09-19 | Magnetization dynamics of the compensated ferrimagnet $Mn_{2}Ru_{x}Ga$ | Here we study both static and time-resolved dynamic magnetic properties of
the compensated ferrimagnet from room temperature down to 10K, thus crossing
the magnetic compensation temperature $T_{M}$. The behaviour is analysed with a
model of a simple collinear ferrimagnet with uniaxial anisotropy and
site-specific gyrom... | 1909.09085v1 |
2019-11-28 | Transport properties of spin superfluids: comparing easy-plane ferro- and antiferromagnets | We present a study on spin-superfluid transport based on an atomistic,
classical spin model. Easy-plane ferro- as well as antiferromagnets are
considered, which allows for a direct comparison of these two material classes
based on the same model assumptions. We find a spin-superfluid transport which
is robust against v... | 1911.12786v1 |
2020-01-17 | Fermi Level Controlled Ultrafast Demagnetization Mechanism in Half-Metallic Heusler Alloy | The electronic band structure-controlled ultrafast demagnetization mechanism
in Co2FexMn1-xSi Heusler alloy is underpinned by systematic variation of
composition. We find the spin-flip scattering rate controlled by spin density
of states at Fermi level is responsible for non-monotonic variation of
ultrafast demagnetiza... | 2001.06217v1 |
2020-04-17 | Collective coordinate study of spin wave emission from dynamic domain wall | We study theoretically the spin wave emission from a moving domain wall in a
ferromagnet. Introducing a deformation mode describing a modulation of the wall
thickness in the collective coordinate description, we show that thickness
variation couples to the spin wave linearly and induces spin wave emission. The
dominant... | 2004.08082v1 |
2021-03-10 | Anisotropic superconducting spin transport at magnetic interfaces | We present a theoretical investigation of anisotropic superconducting spin
transport at a magnetic interface between a p-wave superconductor and a
ferromagnetic insulator. Our formulation describes the ferromagnetic resonance
modulations due to spin current generation depending on spin-triplet Cooper
pair, including th... | 2103.05871v3 |
2022-01-16 | Ferromagnetic resonance modulation in $d$-wave superconductor/ferromagnetic insulator bilayer systems | We investigate ferromagnetic resonance (FMR) modulation in $d$-wave
superconductor (SC)/ferromagnetic insulator (FI) bilayer systems theoretically.
The modulation of the Gilbert damping in these systems reflects the existence
of nodes in the $d$-wave SC and shows power-law decay characteristics within
the low-temperatu... | 2201.06060v2 |
2022-09-28 | Unidirectional magnetic coupling | We show that interlayer Dzyaloshinskii-Moriya interaction in combination with
non-local Gilbert damping gives rise to unidirectional magnetic coupling. That
is, the coupling between two magnetic layers -- say the left and right layer --
is such that dynamics of the left layer leads to dynamics of the right layer,
but n... | 2209.14179v1 |
2023-08-11 | Dynamical Majorana Ising spin response in a topological superconductor-magnet hybrid by microwave irradiation | We study a dynamical spin response of surface Majorana modes in a topological
superconductor-magnet hybrid under microwave irradiation. We find a method to
toggle between dissipative and non-dissipative Majorana Ising spin dynamics by
adjusting the external magnetic field angle and the microwave frequency. This
reflect... | 2308.05955v2 |
2012-10-25 | Decay rates for the damped wave equation on the torus | We address the decay rates of the energy for the damped wave equation when
the damping coefficient $b$ does not satisfy the Geometric Control Condition
(GCC). First, we give a link with the controllability of the associated
Schr\"odinger equation. We prove in an abstract setting that the observability
of the Schr\"odin... | 1210.6879v1 |
2006-10-04 | On the dynamics of spin systems in the Landau-Lifshitz theory | In the framework of the Landau-Lifshitz equations without any dissipation (an
approximation which may also be helpful for finite but weak Gilbert damping),
with all interactions included, for general ground states, geometries and
domain structures, and many types of effective fields the dynamics of the spin
precession ... | 0610122v4 |
2016-04-26 | First principles studies of the Gilbert damping and exchange interactions for half-metallic Heuslers alloys | Heusler alloys have been intensively studied due to the wide variety of
properties that they exhibit. One of these properties is of particular interest
for technological applications, i.e. the fact that some Heusler alloys are
half-metallic. In the following, a systematic study of the magnetic properties
of three diffe... | 1604.07552v1 |
2016-12-21 | Spin Pumping, Dissipation, and Direct and Alternating Inverse Spin Hall Effects in Magnetic Insulator-Normal Metal Bilayers | We theoretically consider the spin-wave mode- and wavelength-dependent
enhancement of the Gilbert damping in magnetic insulator--normal metal bilayers
due to spin pumping as well as the enhancement's relation to direct and
alternating inverse spin Hall voltages in the normal metal. In the
long-wavelength limit, includi... | 1612.07020v2 |
2019-10-29 | Perpendicular magnetic anisotropy in Pt/Co-based full Heusler alloy/MgO thin films structures | Perpendicular magnetic anisotropy (PMA) in ultrathin magnetic structures is a
key ingredient for the development of electrically controlled spintronic
devices. Due to their relatively large spin-polarization, high Curie
temperature and low Gilbert damping the Co-based full Heusler alloys are of
special importance from ... | 1910.13107v1 |
2020-10-15 | Spin injection characteristics of Py/graphene/Pt by gigahertz and terahertz magnetization dynamics driven by femtosecond laser pulse | Spin transport characteristics of graphene has been extensively studied so
far. The spin transport along c-axis is however reported by rather limited
number of papers. We have studied spin transport characteristics through
graphene along c-axis with permalloy(Py)/graphene(Gr)/Pt by gigahertz (GHz) and
terahertz (THz) m... | 2010.07694v1 |
2021-03-17 | Spin injection efficiency at metallic interfaces probed by THz emission spectroscopy | Terahertz (THz) spin-to-charge conversion has become an increasingly
important process for THz pulse generation and as a tool to probe ultrafast
spin interactions at magnetic interfaces. However, its relation to traditional,
steady state, ferromagnetic resonance techniques is poorly understood. Here we
investigate nano... | 2103.09557v1 |
2021-09-13 | Control of magnetization dynamics by substrate orientation in YIG thin films | Yttrium Iron Garnet (YIG) and bismuth (Bi) substituted YIG (Bi0.1Y2.9Fe5O12,
BYG) films are grown in-situ on single crystalline Gadolinium Gallium Garnet
(GGG) substrates [with (100) and (111) orientations] using pulsed laser
deposition (PLD) technique. As the orientation of the Bi-YIG film changes from
(100) to (111),... | 2109.05901v1 |
2022-06-06 | Probing spin dynamics of ultra-thin van der Waals magnets via photon-magnon coupling | Layered van der Waals (vdW) magnets can maintain a magnetic order even down
to the single-layer regime and hold promise for integrated spintronic devices.
While the magnetic ground state of vdW magnets was extensively studied, key
parameters of spin dynamics, like the Gilbert damping, crucial for designing
ultra-fast s... | 2206.02460v2 |
2022-09-01 | Growth parameters of Bi0.1Y2.9Fe5O12 thin films for high frequency applications | The growth and characterization of Bismuth (Bi) substituted YIG (Bi-YIG,
Bi0.1Y2.9Fe5O12) thin films are reported. Pulsed laser deposited (PLD) films
with thicknesses ranging from 20 to 150 nm were grown on Gadolinium Gallium
Garnet substrates. Two substrate orientations of (100) and (111) were
considered. The enhanced... | 2209.00558v1 |
2019-10-17 | Modified different nonlinearities for weakly coupled systems of semilinear effectively damped waves with different time-dependent coefficients in the dissipation terms | We prove the global existence of small data solution in all space dimension
for weakly coupled systems of semi-linear effectively damped wave, with
different time-dependent coefficients in the dissipation terms. Moreover,
nonlinearity terms $ f(t,u) $ and $ g(t,v) $ satisfying some properties of the
parabolic equation.... | 1910.07731v1 |
2021-10-10 | Global existence of solutions for semilinear damped wave equations with variable coefficients | We consider the Cauchy problem for the damped wave equations with variable
coefficients a(x) having power type nonlinearity |u|^p. We discuss the global
existence of solutions for small initial data and investigate the relation
between the range of a(x) and the order p. | 2110.04718v2 |
2023-04-23 | Decay rates for a variable-coefficient wave equation with nonlinear time-dependent damping | In this paper, a class of variable-coefficient wave equations equipped with
time-dependent damping and the nonlinear source is considered. We show that the
total energy of the system decays to zero with an explicit and precise decay
rate estimate under different assumptions on the feedback with the help of the
method o... | 2304.11522v1 |
2019-07-10 | Determination of the damping co-efficient of electrons in optically transparent glasses at the true resonance frequency in the ultraviolet from an analysis of the Lorentz-Maxwell model of dispersion | The Lorentz-Maxwell model of dispersion of light has been analyzed in this
paper to determine the true resonance frequency in the ultraviolet for the
electrons in optically transparent glasses and the damping coefficient at this
frequency. For this we needed the refractive indices of glass in the optical
frequency rang... | 1907.04499v1 |
2012-07-17 | Asymptotic Dynamics of a Class of Coupled Oscillators Driven by White Noises | This paper is devoted to the study of the asymptotic dynamics of a class of
coupled second order oscillators driven by white noises. It is shown that any
system of such coupled oscillators with positive damping and coupling
coefficients possesses a global random attractor. Moreover, when the damping
and the coupling co... | 1207.3864v1 |
2020-09-22 | Sharp exponential decay rates for anisotropically damped waves | In this article, we study energy decay of the damped wave equation on compact
Riemannian manifolds where the damping coefficient is anisotropic and modeled
by a pseudodifferential operator of order zero. We prove that the energy of
solutions decays at an exponential rate if and only if the damping coefficient
satisfies... | 2009.10832v2 |
2017-02-27 | Current Induced Damping of Nanosized Quantum Moments in the Presence of Spin-Orbit Interaction | Motivated by the need to understand current-induced magnetization dynamics at
the nanoscale, we have developed a formalism, within the framework of Keldysh
Green function approach, to study the current-induced dynamics of a
ferromagnetic (FM) nanoisland overlayer on a spin-orbit-coupling (SOC) Rashba
plane. In contrast... | 1702.08408v2 |
2021-06-16 | Spin-Torque-driven Terahertz Auto Oscillations in Non-Collinear Coplanar Antiferromagnets | We theoretically and numerically study the terahertz auto oscillations in
thin-film metallic non-collinear coplanar antiferromagnets (AFMs), such as
$\mathrm{Mn_{3}Sn}$ and $\mathrm{Mn_{3}Ir}$, under the effect of anti-damping
spin-torque with spin polarization perpendicular to the plane of the film. To
obtain the orde... | 2106.08528v2 |
2023-01-30 | Investigation of Ultrafast Demagnetization and Gilbert Damping and their Correlation in Different Ferromagnetic Thin Films Grown Under Identical Conditions | Following the demonstration of laser-induced ultrafast demagnetization in
ferromagnetic nickel, several theoretical and phenomenological propositions
have sought to uncover its underlying physics. In this work we revisit the
three temperature model (3TM) and the microscopic three temperature model
(M3TM) to perform a c... | 2301.12797v1 |
2016-10-01 | The destabilizing effect of external damping: Singular flutter boundary for the Pfluger column with vanishing external dissipation | Elastic structures loaded by nonconservative positional forces are prone to
instabilities induced by dissipation: it is well-known in fact that internal
viscous damping destabilizes the marginally stable Ziegler's pendulum and
Pfluger column (of which the Beck's column is a special case), two structures
loaded by a tan... | 1611.03886v1 |
2018-05-16 | Stabilization rates for the damped wave equation with Hölder-regular damping | We study the decay rate of the energy of solutions to the damped wave
equation in a setup where the geometric control condition is violated. We
consider damping coefficients which are $0$ on a strip and vanish like
polynomials, $x^{\beta}$. We prove that the semigroup cannot be stable at rate
faster than $1/t^{(\beta+2... | 1805.06535v3 |
2014-02-07 | One-dimensional random attractor and rotation number of the stochastic damped sine-Gordon equation | This paper is devoted to the study of the asymptotic dynamics of the
stochastic damped sine-Gordon equation with homogeneous Neumann boundary
condition. It is shown that for any positive damping and diffusion
coefficients, the equation possesses a random attractor, and when the damping
and diffusion coefficients are su... | 1402.1787v1 |
2021-02-01 | Blow-up and lifespan estimates for a damped wave equation in the Einstein-de Sitter spacetime with nonlinearity of derivative type | In this article, we investigate the blow-up for local solutions to a
semilinear wave equation in the generalized Einstein - de Sitter spacetime with
nonlinearity of derivative type. More precisely, we consider a semilinear
damped wave equation with a time-dependent and not summable speed of
propagation and with a time-... | 2102.01137v2 |
2023-10-24 | Frictional weakening of a granular sheared layer due to viscous rolling revealed by Discrete Element Modeling | Considering a 3D sheared granular layer modeled with discrete elements, it is
well known the rolling resistance significantly influences the mechanical
behavior. Even if the rolling resistance role has been deeply investigated as
it is commonly used to represent the the roughness of the grains and the
interparticle loc... | 2310.15945v1 |
2019-04-24 | On the Energy Decay Rate of the Fractional Wave Equation on $\mathbb{R}$ with Relatively Dense Damping | We establish upper bounds for the decay rate of the energy of the damped
fractional wave equation when the averages of the damping coefficient on all
intervals of a fixed length are bounded below. If the power of the fractional
Laplacian, $s$, is between 0 and 2, the decay is polynomial. For $s \ge 2$, the
decay is exp... | 1904.10946v3 |
2021-02-28 | Stability for an inverse source problem of the damped biharmonic plate equation | This paper is concerned with the stability of the inverse source problem for
the damped biharmonic plate equation in three dimensions. The stability
estimate consists of the Lipschitz type data discrepancy and the high frequency
tail of the source function, where the latter decreases as the upper bound of
the frequency... | 2103.00461v1 |
2023-02-13 | Damping of gravitational waves in f(R) gravity | We study the damping of $f(R)$ gravitational waves by matter in flat
spacetime and in expanding universe. In the former case, we find that the
Landau damping of scalar mode in $f(R)$ theory exists, while that of the tensor
mode in general relativity does not; we also present the viscosity coefficients
and dispersion re... | 2302.06402v2 |
2023-03-20 | Nonlinear Damping and Field-aligned Flows of Propagating Shear Alfvén Waves with Braginskii Viscosity | Braginskii MHD provides a more accurate description of many plasma
environments than classical MHD since it actively treats the stress tensor
using a closure derived from physical principles. Stress tensor effects
nonetheless remain relatively unexplored for solar MHD phenomena, especially in
nonlinear regimes. This pa... | 2303.11128v1 |
2024-01-09 | Damping Separation of Finite Open Systems in Gravity-Related Experiments in the Free Molecular Flow Regime | The residual gas damping of the test mass (TM) in the free molecular flow
regime is studied in the finite open systems for high-precision gravity-related
experiments. Through strict derivation, we separate the damping coefficients
for two finite open systems, i.e., the bi-plate system and the sensor core
system, into b... | 2401.04808v1 |
2010-09-20 | Diffusive properties of persistent walks on cubic lattices with application to periodic Lorentz gases | We calculate the diffusion coefficients of persistent random walks on cubic
and hypercubic lattices, where the direction of a walker at a given step
depends on the memory of one or two previous steps. These results are then
applied to study a billiard model, namely a three-dimensional periodic Lorentz
gas. The geometry... | 1009.3922v1 |
2012-11-13 | Critical exponent for the semilinear wave equation with scale invariant damping | In this paper we consider the critical exponent problem for the semilinear
damped wave equation with time-dependent coefficients. We treat the scale
invariant cases. In this case the asymptotic behavior of the solution is very
delicate and the size of coefficient plays an essential role. We shall prove
that if the powe... | 1211.2900v1 |
2010-12-07 | Turbulence damping as a measure of the flow dimensionality | The dimensionality of turbulence in fluid layers determines their properties.
We study electromagnetically driven flows in finite depth fluid layers and show
that eddy viscosity, which appears as a result of three-dimensional motions,
leads to increased bottom damping. The anomaly coefficient, which characterizes
the d... | 1012.1371v1 |
2012-01-05 | Damped bead on a rotating circular hoop - a bifurcation zoo | The evergreen problem of a bead on a rotating hoop shows a multitude of
bifurcations when the bead moves with friction. This motion is studied for
different values of the damping coefficient and rotational speeds of the hoop.
Phase portraits and trajectories corresponding to all different modes of motion
of the bead ar... | 1201.1218v1 |
2015-08-24 | Scaling variables and asymptotic profiles for the semilinear damped wave equation with variable coefficients | We study the asymptotic behavior of solutions for the semilinear damped wave
equation with variable coefficients. We prove that if the damping is effective,
and the nonlinearity and other lower order terms can be regarded as
perturbations, then the solution is approximated by the scaled Gaussian of the
corresponding li... | 1508.05778v3 |
2018-07-17 | On the blow-up for critical semilinear wave equations with damping in the scattering case | We consider the Cauchy problem for semilinear wave equations with variable
coefficients and time-dependent scattering damping in $\mathbf{R}^n$, where
$n\geq 2$. It is expected that the critical exponent will be Strauss' number
$p_0(n)$, which is also the one for semilinear wave equations without damping
terms. Lai and... | 1807.06164v1 |
2013-09-19 | Van der Waals Coefficients for the Alkali-metal Atoms in the Material Mediums | The damping coefficients for the alkali atoms are determined very accurately
by taking into account the optical properties of the atoms and three distinct
types of trapping materials such as Au (metal), Si (semi-conductor) and
vitreous SiO2 (dielectric). Dynamic dipole polarizabilities are calculated
precisely for the ... | 1309.4897v1 |
2001-03-30 | Thermal magnetization fluctuations in thin films and a new physical form for magnetization damping | The effect of thermal fluctuations on a thin film magnetoresistive element
has been calculated. The technique involves adding to the basic spin dynamics a
general form of interaction with a thermal bath. For a general anisotropic
magnetic system the resulting equation can be written as a Langevin equation
for a harmoni... | 0103624v3 |
2004-02-03 | First-principles study of magnetization relaxation enhancement and spin-transfer in thin magnetic films | The interface-induced magnetization damping of thin ferromagnetic films in
contact with normal-metal layers is calculated from first principles for clean
and disordered Fe/Au and Co/Cu interfaces. Interference effects arising from
coherent scattering turn out to be very small, consistent with a very small
magnetic cohe... | 0402088v2 |
2005-02-28 | Magnetization dynamics of two interacting spins in an external magnetic field | The longitudinal relaxation time of the magnetization of a system of two
exchange coupled spins subjected to a strong magnetic field is calculated
exactly by averaging the stochastic Gilbert-Landau-Lifshitz equation for the
magnetization, i.e., the Langevin equation of the process, over its
realizations so reducing the... | 0502661v2 |
2007-06-28 | Coherent Magnetization Precession in GaMnAs induced by Ultrafast Optical Excitation | We use femtosecond optical pulses to induce, control and monitor
magnetization precession in ferromagnetic Ga0.965Mn0.035As. At temperatures
below ~40 K we observe coherent oscillations of the local Mn spins, triggered
by an ultrafast photoinduced reorientation of the in-plane easy axis. The
amplitude saturation of the... | 0706.4270v2 |
2008-02-14 | Light-induced magnetization precession in GaMnAs | We report dynamics of the transient polar Kerr rotation (KR) and of the
transient reflectivity induced by femtosecond laser pulses in ferromagnetic
(Ga,Mn)As with no external magnetic field applied. It is shown that the
measured KR signal consist of several different contributions, among which only
the oscillatory sign... | 0802.2043v2 |
2008-09-17 | Spin-transfer torque induced reversal in magnetic domains | Using the complex stereographic variable representation for the macrospin,
from a study of the nonlinear dynamics underlying the generalized
Landau-Lifshitz(LL) equation with Gilbert damping, we show that the
spin-transfer torque is effectively equivalent to an applied magnetic field. We
study the macrospin switching o... | 0809.2910v1 |
2009-12-30 | Spin torque and critical currents for magnetic vortex nano-oscillator in nanopillars | We calculated the main dynamic parameters of the spin polarized current
induced magnetic vortex oscillations in nanopillars, such as the range of
current density, where a vortex steady oscillations exist, the oscillation
frequency and orbit radius. We accounted for both the non-linear vortex
frequency and non-linear vo... | 0912.5521v1 |
2010-10-01 | Ferromagnetic resonance study of Co/Pd/Co/Ni multilayers with perpendicular anisotropy irradiated with Helium ions | We present a ferromagnetic resonance (FMR) study of the effect of Helium ion
irradiation on the magnetic anisotropy, the linewidth and the Gilbert damping
of a Co/Ni multilayer coupled to Co/Pd bilayers. The perpendicular magnetic
anisotropy decreases linearly with He ion fluence, leading to a transition to
in-plane ma... | 1010.0268v2 |
2010-11-23 | Ultra-fast magnetisation rates within the Landau-Lifshitz-Bloch model | The ultra-fast magnetisation relaxation rates during the laser-induced
magnetisation process are analyzed in terms of the Landau-Lifshitz-Bloch (LLB)
equation for different values of spin $S$. The LLB equation is equivalent in
the limit $S \rightarrow \infty$ to the atomistic Landau-Lifshitz-Gilbert (LLG)
Langevin dyna... | 1011.5054v1 |
2011-10-15 | Atomistic spin dynamic method with both damping and moment of inertia effects included from first principles | We consider spin dynamics for implementation in an atomistic framework and we
address the feasibility of capturing processes in the femtosecond regime by
inclusion of moment of inertia. In the spirit of an {\it s-d} -like interaction
between the magnetization and electron spin, we derive a generalized equation
of motio... | 1110.3387v2 |
2011-10-24 | CoB/Ni-Based Multilayer Nanowire with High-Speed Domain Wall Motion under Low Current Control | The spin-transfer torque motion of magnetic domain walls (DWs) in a
CoB/Ni-based nanowire driven by a low current density of
(1.12\pm0.8)\times10^{11} A m^{-2} has been observed indirectly by
magnetotransport measurements. A high DW velocity of 85\pm4 m/s at zero field
was measured at the threshold current density. Upo... | 1110.5112v3 |
2012-09-17 | Nonlinear emission of spin-wave caustics from an edge mode of a micro-structured Co2Mn0.6Fe0.4Si waveguide | Magnetic Heusler materials with very low Gilbert damping are expected to show
novel magnonic transport phenomena. We report nonlinear generation of higher
harmonics leading to the emission of caustic spin-wave beams in a low-damping,
micro-structured Co2Mn0.6Fe0.4Si Heusler waveguide. The source for the higher
harmonic... | 1209.3669v2 |
2013-07-10 | Scaling of spin Hall angle in 3d, 4d and 5d metals from Y3Fe5O12/metal spin pumping | Pure spin currents generated by spin pumping in ferromagnet/nonmagnet (FM/NM)
bilayers produce inverse spin Hall effect (ISHE) voltages in the NM, from which
spin pumping and transport characteristics of the NM can be extracted. Due to
its exceptionally low damping, Y3Fe5O12 (YIG) is an important and widely used
FM for... | 1307.2648v2 |
2013-11-25 | Spin-wave excitation and propagation in microstructured waveguides of yttrium iron garnet (YIG)/Pt bilayers | We present an experimental study of spin-wave excitation and propagation in
microstructured waveguides patterned from a 100 nm thick yttrium iron garnet
(YIG)/platinum (Pt) bilayer. The life time of the spin waves is found to be
more than an order of magnitude higher than in comparably sized metallic
structures despite... | 1311.6305v1 |
2014-10-02 | Investigation of the temperature-dependence of ferromagnetic resonance and spin waves in Co2FeAl0.5Si0.5 | Co2FeAl0.5Si0.5 (CFAS) is a Heusler compound that is of interest for
spintronics applications, due to its high spin polarization and relatively low
Gilbert damping constant. In this study, the behavior of ferromagnetic
resonance as a function of temperature was investigated in CFAS, yielding a
decreasing trend of dampi... | 1410.0439v1 |
2014-12-12 | Spin waves in micro-structured yttrium iron garnet nanometer-thick films | We investigated the spin-wave propagation in a micro-structured yttrium iron
garnet waveguide of $40$ nm thickness. Utilizing spatially-resolved Brillouin
light scattering microscopy, an exponential decay of the spin-wave amplitude of
$(10.06 \pm 0.83)$ $\mu$m was observed. This leads to an estimated Gilbert
damping co... | 1412.4032v1 |
2016-04-16 | A broadband Ferromagnetic Resonance dipper probe for magnetic damping measurements from 4.2 K to 300 K | A dipper probe for broadband Ferromagnetic Resonance (FMR) operating from 4.2
K to room temperature is described. The apparatus is based on a 2-port
transmitted microwave signal measurement with a grounded coplanar waveguide.
The waveguide generates a microwave field and records the sample response. A
3-stage dipper de... | 1604.04688v1 |
2016-05-27 | A reduced model for precessional switching of thin-film nanomagnets under the influence of spin-torque | We study the magnetization dynamics of thin-film magnetic elements with
in-plane magnetization subject to a spin-current flowing perpendicular to the
film plane. We derive a reduced partial differential equation for the in-plane
magnetization angle in a weakly damped regime. We then apply this model to
study the experi... | 1605.08698v1 |
2016-06-21 | Torsion Effects and LLG Equation | Based on the non-relativistic regime of the Dirac equation coupled to a
torsion pseudo-vector, we study the dynamics of magnetization and how it is
affected by the presence of torsion. We consider that torsion interacting terms
in Dirac equation appear in two ways one of these is thhrough the covariant
derivative consi... | 1606.06610v1 |
2016-07-05 | Magnetic moment of inertia within the breathing model | An essential property of magnetic devices is the relaxation rate in magnetic
switching which strongly depends on the energy dissipation and magnetic inertia
of the magnetization dynamics. Both parameters are commonly taken as a
phenomenological entities. However very recently, a large effort has been
dedicated to obtai... | 1607.01307v1 |
2016-10-14 | Nambu mechanics for stochastic magnetization dynamics | The Landau-Lifshitz-Gilbert (LLG) equation describes the dynamics of a damped
magnetization vector that can be understood as a generalization of Larmor spin
precession. The LLG equation cannot be deduced from the Hamiltonian framework,
by introducing a coupling to a usual bath, but requires the introduction of
addition... | 1610.04598v2 |
2017-01-31 | Lack of correlation between the spin mixing conductance and the ISHE-generated voltages in CoFeB/Pt,Ta bilayers | We investigate spin pumping phenomena in polycrystalline CoFeB/Pt and
CoFeB/Ta bilayers and the correlation between the effective spin mixing
conductance $g^{\uparrow\downarrow}_{\rm eff}$ and the obtained voltages
generated by the spin-to-charge current conversion via the inverse spin Hall
effect in the Pt and Ta laye... | 1701.09110v1 |
2017-06-05 | Consistent microscopic analysis of spin pumping effects | We present a consistent microscopic study of spin pumping effects for both
metallic and insulating ferromagnets. As for metallic case, we present a simple
quantum mechanical picture of the effect as due to the electron spin flip as a
result of a nonadiabatic (off-diagonal) spin gauge field. The effect of
interface spin... | 1706.01185v1 |
2018-03-04 | Optimization of Time-Resolved Magneto-optical Kerr Effect Signals for Magnetization Dynamics Measurements | Recently magnetic storage and magnetic memory have shifted towards the use of
magnetic thin films with perpendicular magnetic anisotropy (PMA). Understanding
the magnetic damping in these materials is crucial, but normal Ferromagnetic
Resonance (FMR) measurements face some limitations. The desire to quantify the
dampin... | 1803.01280v2 |
2018-05-04 | Superparamagnetic Relaxation Driven by Colored Noise | A theoretical investigation of magnetic relaxation processes in single domain
particles driven by colored noise is presented. Two approaches are considered;
the Landau-Lifshitz-Miyazaki-Seki equation, which is a Langevin dynamics model
based on the introduction of an Ornstein-Uhlenbeck correlated noise into the
Landau-... | 1805.01776v2 |
2018-06-02 | Ultra-low damping insulating magnetic thin films get perpendicular | A magnetic material combining low losses and large Perpendicular Magnetic
Anisotropy (PMA) is still a missing brick in the magnonic and spintronic
fields. We report here on the growth of ultrathin Bismuth doped
Y$_{3}$Fe$_{5}$O$_{12}$ (BiYIG) films on Gd$_{3}$Ga$_{5}$O$_{12}$ (GGG) and
substituted GGG (sGGG) (111) orie... | 1806.00658v1 |
2018-06-12 | Dynamical and current-induced Dzyaloshinskii-Moriya interaction: Role for damping, gyromagnetism, and current-induced torques in noncollinear magnets | Both applied electric currents and magnetization dynamics modify the
Dzyaloshinskii-Moriya interaction (DMI), which we call current-induced DMI
(CIDMI) and dynamical DMI (DDMI), respectively. We report a theory of CIDMI and
DDMI. The inverse of CIDMI consists in charge pumping by a time-dependent
gradient of magnetizat... | 1806.04782v3 |
2018-10-11 | Propagating spin waves in nanometer-thick yttrium iron garnet films: Dependence on wave vector, magnetic field strength and angle | We present a comprehensive investigation of propagating spin waves in
nanometer-thick yttrium iron garnet (YIG) films. We use broadband spin-wave
spectroscopy with integrated coplanar waveguides (CPWs) and microstrip antennas
on top of continuous and patterned YIG films to characterize spin waves with
wave vectors up t... | 1810.04973v1 |
2019-05-30 | Predicting New Iron Garnet Thin Films with Perpendicular Magnetic Anisotropy | Perpendicular magnetic anisotropy (PMA) is a necessary condition for many
spintronic applications like spin-orbit torques switching, logic and memory
devices. An important class of magnetic insulators with low Gilbert damping at
room temperature are iron garnets, which only have a few PMA types such as
terbium and sama... | 1905.13042v1 |
2019-07-17 | Inhomogeneous domain walls in spintronic nanowires | In case of a spin-polarized current, the magnetization dynamics in nanowires
are governed by the classical Landau-Lifschitz equation with Gilbert damping
term, augmented by a typically non-variational Slonczewski term. Taking axial
symmetry into account, we study the existence of domain wall type coherent
structure sol... | 1907.07470v2 |
2019-09-10 | Spin Pumping from Permalloy into Uncompensated Antiferromagnetic Co doped Zinc Oxide | Heterostructures of Co-doped ZnO and Permalloy were investigated for their
static and dynamic magnetic interaction. The highly Co-doped ZnO is
paramagentic at room temperature and becomes an uncompensated antiferromagnet
at low temperatures, showing a narrowly opened hysteresis and a vertical
exchange bias shift even i... | 1909.04362v3 |
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