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2022-03-10 | Accelerated gradient methods combining Tikhonov regularization with geometric damping driven by the Hessian | In a Hilbert setting, for convex differentiable optimization, we consider
accelerated gradient dynamics combining Tikhonov regularization with
Hessian-driven damping. The Tikhonov regularization parameter is assumed to
tend to zero as time tends to infinity, which preserves equilibria. The
presence of the Tikhonov regu... | 2203.05457v2 |
2022-08-25 | The Effect of Frequency Droop Damping on System Parameters and Battery Sizing During Load Change Condition | Inverter-based resources (IBR) have been widely studied for their advantages
on the current power systems. This increase in the penetration of renewable
energy has raised some concerns about the stability of the existing grid.
Historically, power systems are dominated by synchronous generators that can
easily react to ... | 2208.12291v1 |
2023-07-28 | Premature jump-down mimicks nonlinear damping in nanoresonators | Recent experiments on nano-resonators in a bistable regime use the
`jump-down' point between states to infer mechanical properties of the membrane
or a load, but often suggest the presence of some nonlinear damping. Motivated
by such experiments, we develop a mechanical model of a membrane subject to a
uniform, oscilla... | 2307.15656v1 |
2023-10-11 | Damping Density of an Absorptive Shoebox Room Derived from the Image-Source Method | The image-source method is widely applied to compute room impulse responses
(RIRs) of shoebox rooms with arbitrary absorption. However, with increasing RIR
lengths, the number of image sources grows rapidly, leading to slow
computation. In this paper, we derive a closed-form expression for the damping
density, which ch... | 2310.07363v1 |
2003-11-17 | Cosmic Ray Scattering by Compressible Magnetohydrodynamic Turbulence | Recent advances in understanding of magnetohydrodynamic (MHD) turbulence call
for substantial revisions in the picture of cosmic ray transport. In this paper
we use recently obtained scaling laws for MHD modes to calculate the scattering
frequency for cosmic rays in the ISM. We consider gyroresonance with MHD modes
(Al... | 0311369v1 |
2010-03-16 | Justification of the symmetric damping model of the dynamical Casimir effect in a cavity with a semiconductor mirror | A "microscopic" justification of the "symmetric damping" model of a quantum
oscillator with time-dependent frequency and time-dependent damping is given.
This model is used to predict results of experiments on simulating the
dynamical Casimir effect in a cavity with a photo-excited semiconductor mirror.
It is shown tha... | 1003.3061v2 |
2022-07-13 | Energy decay for the time dependent damped wave equation | Energy decay is established for the damped wave equation on compact
Riemannian manifolds where the damping coefficient is allowed to depend on
time. Using a time dependent observability inequality, it is shown that the
energy of solutions decays at an exponential rate if the damping coefficient
satisfies a time depende... | 2207.06260v4 |
2022-10-10 | Finite time extinction for a critically damped Schr{ö}dinger equation with a sublinear nonlinearity | This paper completes some previous studies by several authors on the finite
time extinction for nonlinear Schr{\"o}dinger equation when the nonlinear
damping term corresponds to the limit cases of some ``saturating non-Kerr law''
$F(|u|^2)u=\frac{a}{\varepsilon+(|u|^2)^\alpha}u,$ with $a\in\mathbb{C},$
$\varepsilon\geq... | 2210.04493v4 |
2023-12-28 | Cause-effect relationship between model parameters and damping performance of hydraulic shock absorbers | Despite long-term research and development of modern shock absorbers, the
effect of variations of several crucial material and model parameters still
remains dubious. The goal of this work is therefore a study of the changes of
shock absorber dynamics with respect to typical parameter ranges in a realistic
model. We st... | 2312.17175v1 |
2024-01-04 | A Pure Integral-Type PLL with a Damping Branch to Enhance the Stability of Grid-Tied Inverter under Weak Grids | In a phase-locked loop (PLL) synchronized inverter, due to the strong
nonlinear coupling between the PLL's parame-ters and the operation power angle,
the equivalent damping coefficient will quickly deteriorate while the power
angle is close to 90{\deg} under an ultra-weak grid, which causes the
synchronous instability.... | 2401.02202v1 |
2024-01-16 | Waves in strong centrifugal filed: dissipative gas | In the fast rotating gas (with the velocity typical for Iguassu gas
centrifuge) three families of linear waves exist with different polarizations
and law of dispersion. The energy of the waves is basically concentrated at the
axis of rotation in the rarefied region. Therefore these waves decay on the
distance comparabl... | 2401.08240v1 |
2024-01-19 | Upper bound of the lifespan of the solution to the nonlinear fractional wave equations with time-dependent damping | In this paper, we study the Cauchy problem of the nonlinear wave equation
with fractional Laplacian and time-dependent damping. Firstly, we derive the
weighted Sobolev estimate of the solution operators for the linear wave
equation with the damping of constant coefficient, and prove the local
existence and uniqueness i... | 2401.10552v1 |
2014-01-08 | Dynamic exchange via spin currents in acoustic and optical modes of ferromagnetic resonance in spin-valve structures | Two ferromagnetic layers magnetically decoupled by a thick normal metal
spacer layer can be, nevertheless, dynamically coupled via spin currents
emitted by the spin-pump and absorbed through the spin-torque effects at the
neighboring interfaces. A decrease of damping in both layers due to a partial
compensation of the ... | 1401.1672v1 |
2020-08-29 | Exploring a quantum-information-relevant magnonic material: Ultralow damping at low temperature in the organic ferrimagnet V[TCNE]x | Quantum information science and engineering requires novel low-loss magnetic
materials for magnon-based quantum-coherent operations. The search for low-loss
magnetic materials, traditionally driven by applications in microwave
electronics near room-temperature, has gained additional constraints from the
need to operate... | 2008.13061v3 |
2011-09-08 | On the attenuation coefficient of monomode periodic waveguides | It is widely accepted that, on ensemble average, the transmission T of guided
modes decays exponentially with the waveguide length L due to small
imperfections, leading to the important figure of merit defined as the
attenuation-rate coefficient alpha = -<ln(T)>/L. In this letter, we evidence
that the exponential-dampi... | 1109.1642v1 |
2011-12-31 | Stability of cnoidal waves in the parametrically driven nonlinear Schrödinger equation | The parametrically driven, damped nonlinear Schr\"odinger equation has two
cn- and two dn-wave solutions. We show that one pair of the cn and dn solutions
is unstable for any combination of the driver's strength, dissipation
coefficient and spatial period of the wave; this instability is against
periodic perturbations.... | 1201.0263v1 |
2016-04-20 | Reconstruction for multiwave imaging in attenuating media with large damping coefficient | In this article we study the reconstruction problem in TAT/PAT on an
attenuating media. Namely, we prove a reconstruction procedure of the initial
condition for the damped wave equation via Neumann series that works for
arbitrary large smooth attenuation coefficients extending the result of Homan
in [1]. We also illust... | 1604.06068v3 |
2016-09-20 | H{ö}lder stability in determining the potential and the damping coefficient in a wave equation | We improve the preceding results obtained by the first and the second authors
in [3]. They concern the stability issue of the inverse problem that consists
in determining the potential and the damping coefficient in a wave equation
from an initial-to-boundary operator. We partially modify the arguments in [3]
to show t... | 1609.06102v1 |
2021-11-30 | Determining damping terms in fractional wave equations | This paper deals with the inverse problem of recovering an arbitrary number
of fractional damping terms in a wave equation. We develop several approaches
on uniqueness and reconstruction, some of them relying on Tauberian theorems on
the relation between the asymptotics of solutions in time and Laplace domain.
Also the... | 2112.00080v2 |
2023-06-28 | Global solutions and blow-up for the wave equation with variable coefficients: II. boundary supercritical source | In this paper, we consider the wave equation with variable coefficients and
boundary damping and supercritical source terms. The goal of this work is
devoted to prove the local and global existence, and classify decay rate of
energy depending on the growth near zero on the damping term. Moreover, we
prove the blow-up o... | 2306.15897v4 |
2023-07-29 | An inverse problem for the fractionally damped wave equation | We consider an inverse problem for a Westervelt type nonlinear wave equation
with fractional damping. This equation arises in nonlinear acoustic imaging,
and we show the forward problem is locally well-posed. We prove that the smooth
coefficient of the nonlinearity can be uniquely determined, based on the
knowledge of ... | 2307.16065v1 |
2011-11-09 | Stabilization by switching control methods | In this paper we consider some stabilization problems for the wave equation
with switching. We prove exponential stability results for appropriate damping
coefficients. The proof of the main results is based on D'Alembert formula and
some energy estimates. | 1111.2171v1 |
2015-03-31 | Existence of the global attractor for the plate equation with nonlocal nonlinearity in R^{n} | We consider Cauchy problem for the semilinear plate equation with nonlocal
nonlinearity. Under mild conditions on the damping coefficient, we prove that
the semigroup generated by this problem possesses a global attractor. | 1503.09123v1 |
2021-03-29 | Nonequilibrium Dynamics of the Chiral Quark Condensate under a Strong Magnetic Field | Strong magnetic fields impact quantum-chromodynamics (QCD) properties in
several situations; examples include the early universe, magnetars, and
heavy-ion collisions. These examples share a common trait: time evolution. A
prominent QCD property impacted by a strong magnetic field is the quark
condensate, an approximate... | 2103.15665v1 |
2003-04-18 | Elementary Excitations of Ferromagnetic Metal Nanoparticles | We present a theory of the elementary spin excitations in transition metal
ferromagnet nanoparticles which achieves a unified and consistent quantum
description of both collective and quasiparticle physics. The theory starts by
recognizing the essential role played by spin-orbit interactions in determining
the energies... | 0304427v1 |
2014-08-02 | Tunnel magnetoresistance and spin-transfer-torque switching in polycrystalline Co2FeAl full-Heusler alloy magnetic tunnel junctions on Si/SiO2 amorphous substrates | We studied polycrystalline B2-type Co2FeAl (CFA) full-Heusler alloy based
magnetic tunnel junctions (MTJs) fabricated on a Si/SiO2 amorphous substrate.
Polycrystalline CFA films with a (001) orientation, a high B2 ordering, and a
flat surface were achieved using a MgO buffer layer. A tunnel magnetoresistance
(TMR) rati... | 1408.0341v1 |
2018-02-20 | Ultrafast magnetization dynamics in pure and doped Heusler and inverse Heusler alloys | By using a multiscale approach based on first-principles density functional
theory combined with atomistic spin dynamics, we investigate the electronic
structure and magnetization dynamics of an inverse Heusler and a Heusler
compound and their alloys, i. e. Mn$_{2-x}Z_x$CoAl and Mn$_{2-x}Z_x$VAl, where
$Z$ = Mo, W, Os ... | 1802.07195v1 |
2018-04-10 | GONG Catalog of Solar Filament Oscillations Near Solar Maximum | We have catalogued 196 filament oscillations from the GONG $H{\alpha}$
network data during several months near the maximum of solar cycle 24 (January
- June 2014). Selected examples from the catalog are described in detail, along
with our statistical analyses of all events. Oscillations were classified
according to the... | 1804.03743v1 |
2018-10-16 | Spin-wave-induced lateral temperature gradient in a YIG thin film/GGG system excited in an ESR cavity | Lateral thermal gradient of an yttrium iron garnet (YIG) film under the
microwave application in the cavity of the electron spin resonance system (ESR)
was measured at room temperature by fabricating a Cu/Sb thermocouple onto it.
To date, thermal transport in YIG films caused by the Damon-Eshbach mode (DEM)
- the unidi... | 1810.06875v1 |
2021-08-24 | Shape anisotropy effect on magnetization reversal induced by linear down chirp pulse | We investigate the influence of shape anisotropy on the magnetization
reversal of a single-domain magnetic nanoparticle driven by a circularly
polarized linear down-chirp microwave field pulse (DCMP). Based on the
Landau-Lifshitz-Gilbert equation, numerical results show that the three
controlling parameters of DCMP, na... | 2108.10965v2 |
2021-11-23 | Resonant dynamics of skyrmion lattices in thin film multilayers: Localised modes and spin wave emission | The spectral signatures of magnetic skyrmions under microwave field
excitation are of fundamental interest and can be an asset for high frequency
applications. These topological solitons can be tailored in multilayered thin
films, but the experimental observation of their spin wave dynamics remains
elusive, in particul... | 2111.11797v2 |
2022-05-20 | Effects of Crystalline Disorder on Interfacial and Magnetic Properties of Sputtered Topological Insulator/Ferromagnet Heterostructures | Thin films of Topological insulators (TIs) coupled with ferromagnets (FMs)
are excellent candidates for energy-efficient spintronics devices. Here, the
effect of crystalline structural disorder of TI on interfacial and magnetic
properties of sputter-deposited TI/FM, Bi2Te3/Ni80Fe20, heterostructures is
reported. Ni and... | 2205.09913v1 |
2022-12-24 | Anatomy of ultrafast quantitative magneto-acoustics in freestanding nickel thin films | We revisit the quantitative analysis of the ultrafast magneto-acoustic
experiment in a freestanding nickel thin film by Kim and Bigot [1] by applying
our recently proposed approach of magnetic and acoustic eigenmodes
decomposition by Vernik et al. [2]. We show that the application of our
modeling to the analysis of tim... | 2212.12673v1 |
2023-05-16 | Non-Hermitian Casimir Effect of Magnons | There has been a growing interest in non-Hermitian quantum mechanics. The key
concepts of quantum mechanics are quantum fluctuations. Quantum fluctuations of
quantum fields confined in a finite-size system induce the zero-point energy
shift. This quantum phenomenon, the Casimir effect, is one of the most striking
pheno... | 2305.09231v1 |
2008-02-21 | Gas Damping Coefficient Research for MEMS Comb Linear Vibration Gyroscope | Silicon-MEMS gyroscope is an important part of MEMS (Micro Electrical
Mechanical System). There are some disturb ignored in traditional gyroscope
that must be evaluated newly because of its smaller size (reach the level of
micron). In these disturb, the air pressure largely influences the performance
of MEMS gyroscope.... | 0802.3048v1 |
2008-11-13 | Higher order energy decay rates for damped wave equations with variable coefficients | Under appropriate assumptions the energy of wave equations with damping and
variable coefficients $c(x)u_{tt}-\hbox{div}(b(x)\nabla u)+a(x)u_t =h(x)$ has
been shown to decay. Determining the rate of decay for the higher order
energies involving the $k$th order spatial and time derivatives has been an
open problem with ... | 0811.2159v1 |
2009-05-13 | Time-dependent barrier passage of Two-dimensional non-Ohmic damping system | The time-dependent barrier passage of an anomalous damping system is studied
via the generalized Langevin equation (GLE) with non-Ohmic memory damping
friction tensor and corresponding thermal colored noise tensor describing a
particle passing over the saddle point of a two-dimensional quadratic potential
energy surfac... | 0905.2074v1 |
2011-07-11 | One-dimensional vertical dust strings in a glass box | The oscillation spectrum of a one-dimensional vertical dust string formed
inside a glass box on top of the lower electrode in a GEC reference cell was
studied. A mechanism for creating a single vertical dust string is described.
It is shown that the oscillation amplitudes, resonance frequencies, damping
coefficients, a... | 1107.2074v1 |
2016-02-24 | Pressure of a gas of underdamped active dumbbells | The pressure exerted on a wall by a gas at equilibrium does not depend on the
shape of the confining potential defining the wall. In contrast, it has been
shown recently [A.P. Solon et al., Nat. Phys. 11, 673 (2015)] that a gas of
overdamped active particles exerts on a wall a force that depends on the
confining potent... | 1602.07420v1 |
2016-03-31 | Recovery of time-dependent damping coefficients and potentials appearing in wave equations from partial data | We consider the inverse problem of determining a time-dependent damping
coefficient $a$ and a time-dependent potential $q$, appearing in the wave
equation $\partial_t^2u-\Delta_x u+a(t,x)\partial_tu+q(t,x)u=0$ in
$Q=(0,T)\times\Omega$, with $T>0$ and $\Omega$ a $ \mathcal C^2$ bounded domain
of $\mathbb R^n$, $n\geq2$,... | 1603.09600v2 |
2020-05-04 | Remarks on asymptotic order for the linear wave equation with the scale-invariant damping and mass with $L^r$-data | In the present paper, we consider the linear wave equation with the
scale-invariant damping and mass. It is known that the global behavior of the
solution depends on the size of the coefficients in front of the damping and
mass at initial time $t=0$. Indeed, the solution satisfies the similar decay
estimate to that of ... | 2005.01335v2 |
2023-06-18 | Partial data inverse problem for hyperbolic equation with time-dependent damping coefficient and potential | We study an inverse problem of determining a time-dependent damping
coefficient and potential appearing in the wave equation in a compact
Riemannian manifold of dimension three or higher. More specifically, we are
concerned with the case of conformally transversally anisotropic manifolds, or
in other words, compact Rie... | 2306.10442v2 |
2013-03-14 | Drag and Diffusion coefficients in extreme scenarios of temperature and chemical potential | A comparative study of high and zero temperature plasma for the case of
damping rate, drag and diffusion coefficients have been presented. In each of
these quantities, it is revealed how the magnetic interaction dominates over
the electric one at zero temperature unlike what happens at high temperature. | 1303.3353v1 |
2002-09-07 | Neural network analysis of the magnetization reversal in magnetic dot arrays | We simulated the remagnetization dynamics of the ultra-dense and ultra-thin
magnetic dot array system with dipole-dipole and exchange coupling
interactions. Within the proposed 2D XY superlattice model, the square dots are
modeled by the spatially modulated exchange-couplings. The dipole-dipole
interactions were approx... | 0209186v1 |
2005-04-06 | Macrospin Models of Spin Transfer Dynamics | The current-induced magnetization dynamics of a spin valve are studied using
a macrospin (single domain) approximation and numerical solutions of a
generalized Landau-Lifshitz-Gilbert equation. For the purpose of quantitative
comparison with experiment [Kiselev {\it et al.} Nature {\bf 425}, 380 (2003)],
we calculate t... | 0504142v1 |
2006-02-01 | Mapping Monte Carlo to Langevin dynamics: A Fokker-Planck approach | We propose a general method of using the Fokker-Planck equation (FPE) to link
the Monte-Carlo (MC) and the Langevin micromagnetic schemes. We derive the
drift and disusion FPE terms corresponding to the MC method and show that it is
analytically equivalent to the stochastic Landau-Lifshitz-Gilbert (LLG)
equation of Lan... | 0602011v2 |
2006-04-21 | Dynamic approach for micromagnetics close to the Curie temperature | In conventional micromagnetism magnetic domain configurations are calculated
based on a continuum theory for the magnetization which is assumed to be of
constant length in time and space. Dynamics is usually described with the
Landau-Lifshitz-Gilbert (LLG) equation the stochastic variant of which includes
finite temper... | 0604508v1 |
2007-02-20 | Spin dynamics in a superconductor / ferromagnet proximity system | The ferromagnetic resonance of thin sputtered Ni80Fe20 films grown on Nb is
measured. By varying the temperature and thickness of the Nb the role of the
superconductivity on the whole ferromagnetic layer in these heterostructures is
explored. The change in the spin transport properties below the superconducting
transit... | 0702461v1 |
2007-02-21 | Domain wall mobility, stability and Walker breakdown in magnetic nanowires | We present an analytical calculation of the velocity of a single 180 degree
domain wall in a magnetic structure with reduced thickness and/or lateral
dimension under the combined action of an external applied magnetic field and
an electrical current. As for the case of field-induced domain wall propagation
in thick fil... | 0702492v1 |
2001-01-09 | Hysteresis in layered spring magnets | This article addresses a problem of micromagnetics: the reversal of magnetic
moments in layered spring magnets. A one-dimensional model is used of a film
consisting of several atomic layers of a soft material on top of several atomic
layers of a hard material. Each atomic layer is taken to be uniformly
magnetized, and ... | 0101077v1 |
2005-01-01 | Equatorial and related non-equilibrium states in magnetization dynamics of ferromagnets: Generalization of Suhl's spin-wave instabilities | We investigate the nonlinear dynamics underlying the evolution of a 2-D
nanoscale ferromagnetic film with uniaxial anisotropy in the presence of
perpendicular pumping. Considering the associated Landau-Lifshitz spin
evolution equation with Gilbert damping together with Maxwell equation for the
demagnetization field, we... | 0501002v2 |
2002-12-30 | Stochastic resonance in periodic potentials: realization in a dissipative optical lattice | We have observed the phenomenon of stochastic resonance on the Brillouin
propagation modes of a dissipative optical lattice. Such a mode has been
excited by applying a moving potential modulation with phase velocity equal to
the velocity of the mode. Its amplitude has been characterized by the
center-of-mass (CM) veloc... | 0212156v1 |
2007-05-03 | Planar spin-transfer device with a dynamic polarizer | In planar nano-magnetic devices magnetization direction is kept close to a
given plane by the large easy-plane magnetic anisotropy, for example by the
shape anisotropy in a thin film. In this case magnetization shows effectively
in-plane dynamics with only one angle required for its description. Moreover,
the motion ca... | 0705.0406v1 |
2007-05-03 | Effective attraction induced by repulsive interaction in a spin-transfer system | In magnetic systems with dominating easy-plane anisotropy the magnetization
can be described by an effective one dimensional equation for the in-plane
angle. Re-deriving this equation in the presence of spin-transfer torques, we
obtain a description that allows for a more intuitive understanding of
spintronic devices' ... | 0705.0508v1 |
2007-06-21 | Spin pumping by a field-driven domain wall | We calculate the charge current in a metallic ferromagnet to first order in
the time derivative of the magnetization direction. Irrespective of the
microscopic details, the result can be expressed in terms of the conductivities
of the majority and minority electrons and the non-adiabatic spin transfer
torque parameter ... | 0706.3160v3 |
2007-09-18 | Theory of current-driven magnetization dynamics in inhomogeneous ferromagnets | We give a brief account of recent developments in the theoretical
understanding of the interaction between electric currents and inhomogeneous
ferromagnetic order parameters. We start by discussing the physical origin of
the spin torques responsible for this interaction and construct a
phenomenological description. We ... | 0709.2937v2 |
2008-02-12 | Temperature dependent magnetization dynamics of magnetic nanoparticles | Recent experimental and theoretical studies show that the switching behavior
of magnetic nanoparticles can be well controlled by external time-dependent
magnetic fields. In this work, we inspect theoretically the influence of the
temperature and the magnetic anisotropy on the spin-dynamics and the switching
properties ... | 0802.1740v1 |
2008-09-25 | The theory of magnetic field induced domain-wall propagation in magnetic nanowires | A global picture of magnetic domain wall (DW) propagation in a nanowire
driven by a magnetic field is obtained: A static DW cannot exist in a
homogeneous magnetic nanowire when an external magnetic field is applied. Thus,
a DW must vary with time under a static magnetic field. A moving DW must
dissipate energy due to t... | 0809.4311v1 |
2008-10-08 | Transverse spin diffusion in ferromagnets | We discuss the dissipative diffusion-type term of the form
$\mathbf{m}\times\nabla^2\partial_t\mathbf{m}$ in the phenomenological
Landau-Lifshitz equation of ferromagnetic precession, which describes enhanced
Gilbert damping of finite-momentum spin waves. This term arises physically from
itinerant-electron spin flows t... | 0810.1340v2 |
2008-10-16 | Interaction of reed and acoustic resonator in clarinetlike systems | Sound emergence in clarinetlike instruments is investigated in terms of
instability of the static regime. Various models of reed-bore coupling are
considered, from the pioneering work of Wilson and Beavers ["Operating modes of
the clarinet", J. Acoust. Soc. Am. 56, 653--658 (1974)] to more recent modeling
including vis... | 0810.2870v1 |
2008-11-21 | Spin Transfer Torque as a Non-Conservative Pseudo-Field | In this paper we show that the spin transfer torque can be described by a
pseudo magnetic field, proportional to the magnetic moment of the itinerant
electrons that enters the Landau-Lifshitz-Gilbert equation in the same way as
other external or internal magnetic fields. However, unlike an ordinary
magnetic field, whic... | 0811.3472v1 |
2008-12-13 | Non-Adiabatic Spin Transfer Torque in Real Materials | The motion of simple domain walls and of more complex magnetic textures in
the presence of a transport current is described by the
Landau-Lifshitz-Slonczewski (LLS) equations. Predictions of the LLS equations
depend sensitively on the ratio between the dimensionless material parameter
$\beta$ which characterizes non-ad... | 0812.2570v1 |
2009-05-29 | Ferromagnetic resonance linewidth in ultrathin films with perpendicular magnetic anisotropy | Transition metal ferromagnetic films with perpendicular magnetic anisotropy
(PMA) have ferromagnetic resonance (FMR) linewidths that are one order of
magnitude larger than soft magnetic materials, such as pure iron (Fe) and
permalloy (NiFe) thin films. A broadband FMR setup has been used to investigate
the origin of th... | 0905.4779v2 |
2009-10-01 | Spin motive forces and current fluctuations due to Brownian motion of domain walls | We compute the power spectrum of the noise in the current due to spin motive
forces by a fluctuating domain wall. We find that the power spectrum of the
noise in the current is colored, and depends on the Gilbert damping, the spin
transfer torque parameter $\beta$, and the domain-wall pinning potential and
magnetic ani... | 0910.0163v1 |
2009-10-08 | Fast domain wall propagation under an optimal field pulse in magnetic nanowires | We investigate field-driven domain wall (DW) propagation in magnetic
nanowires in the framework of the Landau-Lifshitz-Gilbert equation. We propose
a new strategy to speed up the DW motion in a uniaxial magnetic nanowire by
using an optimal space-dependent field pulse synchronized with the DW
propagation. Depending on ... | 0910.1477v2 |
2009-11-24 | Origin of adiabatic and non-adiabatic spin transfer torques in current-driven magnetic domain wall motion | A consistent theory to describe the correlated dynamics of quantum mechanical
itinerant spins and semiclassical local magnetization is given. We consider the
itinerant spins as quantum mechanical operators, whereas local moments are
considered within classical Lagrangian formalism. By appropriately treating
fluctuation... | 0911.4628v1 |
2010-01-26 | Strategies and tolerances of spin transfer torque switching | Schemes of switching nanomagnetic memories via the effect of spin torque with
various polarizations of injected electrons are studied. Simulations based on
macrospin and micromagnetic theories are performed and compared. We demonstrate
that switching with perpendicularly polarized current by short pulses and free
prece... | 1001.4578v1 |
2010-03-31 | Magnonic Crystal with Two-Dimensional Periodicity as a Waveguide for Spin Waves | We describe a simple method of including dissipation in the spin wave band
structure of a periodic ferromagnetic composite, by solving the Landau-Lifshitz
equation for the magnetization with the Gilbert damping term. We use this
approach to calculate the band structure of square and triangular arrays of Ni
nanocylinder... | 1003.6092v1 |
2010-07-20 | Precessing vortices and antivortices in ferromagnetic elements | A micromagnetic numerical study of the precessional motion of the vortex and
antivortex states in soft ferromagnetic circular nanodots is presented using
Landau-Lifshitz-Gilbert dynamics. For sufficiently small dot thickness and
diameter, the vortex state is metastable and spirals toward the center of the
dot when its ... | 1007.3508v1 |
2010-10-07 | Power optimization for domain wall motion in ferromagnetic nanowires | The current mediated domain-wall dynamics in a thin ferromagnetic wire is
investigated. We derive the effective equations of motion of the domain wall.
They are used to study the possibility to optimize the power supplied by
electric current for the motion of domain walls in a nanowire. We show that a
certain resonant ... | 1010.1537v1 |
2011-03-30 | Spin motive forces due to magnetic vortices and domain walls | We study spin motive forces, i.e, spin-dependent forces, and voltages induced
by time-dependent magnetization textures, for moving magnetic vortices and
domain walls. First, we consider the voltage generated by a one-dimensional
field-driven domain wall. Next, we perform detailed calculations on
field-driven vortex dom... | 1103.5858v3 |
2011-07-04 | Influence of randomness and retardation on the FMR-linewidth | The theory predicts that the spin-wave lifetime $\tau_L$ and the linewidth of
ferromagnetic resonance $\Delta B$ can be governed by random fields and spatial
memory. To that aim the effective field around which the magnetic moments
perform a precession is superimposed by a stochastic time dependent magnetic
field with ... | 1107.0638v1 |
2011-11-18 | Charge and Spin Transport in Magnetic Tunnel Junctions: Microscopic Theory | We study the charge and spin currents passing through a magnetic tunnel
junction (MTJ) on the basis of a tight-binding model. The currents are
evaluated perturbatively with respect to the tunnel Hamiltonian. The charge
current has the form $A[\bm M_1(t)\times\dot{\bm M}_1(t)]\cdot\bm M_2+B\dot{\bm
M}_1(t)\cdot\bm M_2$,... | 1111.4295v2 |
2012-01-17 | Magnetic vortex echoes: application to the study of arrays of magnetic nanostructures | We propose the use of the gyrotropic motion of vortex cores in nanomagnets to
produce a magnetic echo, analogous to the spin echo in NMR. This echo occurs
when an array of nanomagnets, e.g., nanodisks, is magnetized with an in-plane
(xy) field, and after a time \tau a field pulse inverts the core magnetization;
the ech... | 1201.3553v1 |
2012-02-15 | Current-induced motion of a transverse magnetic domain wall in the presence of spin Hall effect | We theoretically study the current-induced dynamics of a transverse magnetic
domain wall in bi-layer nanowires consisting of a ferromagnet on top of a
nonmagnet having strong spin-orbit coupling. Domain wall dynamics is
characterized by two threshold current densities, $J_{th}^{WB}$ and
$J_{th}^{REV}$, where $J_{th}^{W... | 1202.3450v1 |
2012-04-23 | Rotating skyrmion lattices by spin torques and field or temperature gradients | Chiral magnets like MnSi form lattices of skyrmions, i.e. magnetic whirls,
which react sensitively to small electric currents j above a critical current
density jc. The interplay of these currents with tiny gradients of either the
magnetic field or the temperature can induce a rotation of the magnetic pattern
for j>jc.... | 1204.5051v1 |
2012-07-09 | Thermal vortex dynamics in thin circular ferromagnetic nanodisks | The dynamics of gyrotropic vortex motion in a thin circular nanodisk of soft
ferromagnetic material is considered. The demagnetization field is calculated
using two-dimensional Green's functions for the thin film problem and fast
Fourier transforms. At zero temperature, the dynamics of the
Landau-Lifshitz-Gilbert equat... | 1207.2192v2 |
2013-02-19 | Chirality Sensitive Domain Wall Motion in Spin-Orbit Coupled Ferromagnets | Using the Lagrangian formalism, we solve analytically the equations of motion
for current-induced domain-wall dynamics in a ferromagnet with Rashba
spin-orbit coupling. An exact solution for the domain wall velocity is
provided, including the effect of non-equilibrium conduction electron
spin-density, Gilbert damping, ... | 1302.4744v1 |
2013-12-17 | Control of the in-plane anisotropy in off-stoichiometric NiMnSb | NiMnSb is a ferromagnetic half-metal which, because of its rich anisotropy
and very low Gilbert damping, is a promising candidate for applications in
information technologies. We have investigated the in-plane anisotropy
properties of thin, MBE-grown NiMnSb films as a function of their Mn
concentration. Using ferromagn... | 1312.4781v2 |
2014-05-09 | Current-induced magnetization dynamics in two magnetic insulators separated by a normal metal | We study the dynamics of spin valves consisting of two layers of magnetic
insulators separated by a normal metal in the macrospin model. A current
through the spacer generates a spin Hall current that can actuate the
magnetization via the spin-transfer torque. We derive expressions for the
effective Gilbert damping and... | 1405.2267v1 |
2014-05-25 | Spin Hall phenomenology of magnetic dynamics | We study the role of spin-orbit interactions in the coupled magnetoelectric
dynamics of a ferromagnetic film coated with an electrical conductor. While the
main thrust of this work is phenomenological, several popular simple models are
considered microscopically in some detail, including Rashba and Dirac
two-dimensiona... | 1405.6354v2 |
2014-08-21 | Brownian motion of massive skyrmions forced by spin polarized currents | We report on the thermal effects on the motion of current-driven massive
magnetic skyrmions. The reduced equation for the motion of skyrmion has the
form of a stochastic generalized Thiele's equation. We propose an ansatz for
the magnetization texture of a non-rigid single skyrmion that depends linearly
with the veloci... | 1408.4861v2 |
2014-11-11 | Capturing of a Magnetic Skyrmion with a Hole | Magnetic whirls in chiral magnets, so-called skyrmions, can be manipulated by
ultrasmall current densities. Here we study both analytically and numerically
the interactions of a single skyrmion in two dimensions with a small hole in
the magnetic layer. Results from micromagnetic simulations are in good
agreement with e... | 1411.2857v1 |
2014-12-01 | Dissipation due to pure spin-current generated by spin pumping | Based on spin-dependent transport theory and thermodynamics, we develop a
generalized theory of the Joule heating in the presence of a spin current.
Along with the conventional Joule heating consisting of an electric current and
electrochemical potential, it is found that the spin current and spin
accumulation give an ... | 1412.0688v1 |
2015-01-30 | Head-to-Head Domain Wall Structures in Wide Permalloy Strips | We analyze the equilibrium micromagnetic domain wall structures encountered
in Permalloy strips of a wide range of thicknesses and widths, with strip
widths up to several micrometers. By performing an extensive set of
micromagnetic simulations, we show that the equilibrium phase diagram of the
domain wall structures ex... | 1501.07731v1 |
2015-02-19 | Characterization of spin relaxation anisotropy in Co using spin pumping | Ferromagnets are believed to exhibit strongly anisotropic spin relaxation,
with relaxation lengths for spin longitudinal to magnetization significantly
longer than those for spin transverse to magnetization. Here we characterize
the anisotropy of spin relaxation in Co using the spin pumping contribution to
Gilbert damp... | 1502.05687v3 |
2015-04-01 | Multiscale modeling of ultrafast element-specific magnetization dynamics of ferromagnetic alloys | A hierarchical multiscale approach to model the magnetization dynamics of
ferromagnetic ran- dom alloys is presented. First-principles calculations of
the Heisenberg exchange integrals are linked to atomistic spin models based
upon the stochastic Landau-Lifshitz-Gilbert (LLG) equation to calculate
temperature-dependent... | 1504.00199v1 |
2015-05-04 | High-topological-number magnetic skyrmions and topologically protected dissipative structure | The magnetic skyrmion with the topological number of unity ($Q=1$) is a
well-known nanometric swirling spin structure in the nonlinear $\sigma$ model
with the Dzyaloshinskii-Moriya interaction. Here, we show that magnetic
skyrmion with the topological number of two ($Q=2$) can be created and
stabilized by applying vert... | 1505.00522v2 |
2015-08-06 | Large spin-wave bullet in a ferrimagnetic insulator driven by spin Hall effect | Due to its transverse nature, spin Hall effects (SHE) provide the possibility
to excite and detect spin currents and magnetization dynamics even in magnetic
insulators. Magnetic insulators are outstanding materials for the investigation
of nonlinear phenomena and for novel low power spintronics applications because
of ... | 1508.01427v1 |
2015-12-02 | Bose-Einstein Condensation of Magnons Pumped by the Bulk Spin Seebeck Effect | We propose inducing Bose-Einstein condensation of magnons in a magnetic
insulator by a heat flow oriented toward its boundary. At a critical heat flux,
the oversaturated thermal gas of magnons accumulated at the boundary
precipitates the condensate, which then grows gradually as the thermal bias is
dialed up further. T... | 1512.00557v1 |
2016-01-10 | Interfacial Dzyaloshinskii-Moriya interaction, surface anisotropy energy,and spin pumping at spin orbit coupled Ir/Co interface | The interfacial Dzyaloshinskii-Moriya interaction (iDMI), surface anisotropy
energy, and spin pumping at the Ir/Co interface are experimentally investigated
by performing Brillouin light scattering. Contrary to previous reports, we
suggest that the sign of the iDMI at the Ir/Co interface is the same as in the
case of t... | 1601.02210v3 |
2016-02-23 | Relaxation of a classical spin coupled to a strongly correlated electron system | A classical spin which is antiferromagnetically coupled to a system of
strongly correlated conduction electrons is shown to exhibit unconventional
real-time dynamics which cannot be described by Gilbert damping. Depending on
the strength of the local Coulomb interaction, the two main electronic
dissipation channels, tr... | 1602.07317v2 |
2016-05-12 | Classical limit of Rabi nutations in spins of ferromagnets | Rabi oscillations describe the interaction of a two-level system with a
rotating electromagnetic field. As such, they serve as the principle method for
manipulating quantum bits. By using a combination of femtosecond laser pulses
and microwave excitations, we have observed the classical form of Rabi
nutations in a ferr... | 1605.03996v1 |
2016-06-07 | The temperature dependence of FeRh's transport properties | The finite-temperature transport properties of FeRh compounds are
investigated by first-principles Density Functional Theory-based calculations.
The focus is on the behavior of the longitudinal resistivity with rising
temperature, which exhibits an abrupt decrease at the metamagnetic transition
point, $T = T_m$ between... | 1606.02072v1 |
2016-09-05 | Coarsening dynamics of topological defects in thin Permalloy films | We study the dynamics of topological defects in the magnetic texture of
rectangular Permalloy thin film elements during relaxation from random
magnetization initial states. Our full micromagnetic simulations reveal complex
defect dynamics during relaxation towards the stable Landau closure domain
pattern, manifested as... | 1609.01094v1 |
2016-09-27 | Anomalous Feedback and Negative Domain Wall Resistance | Magnetic induction can be regarded as a negative feedback effect, where the
motive-force opposes the change of magnetic flux that generates the
motive-force. In artificial electromagnetics emerging from spintronics,
however, this is not necessarily the case. By studying the current-induced
domain wall dynamics in a cyl... | 1609.08250v1 |
2016-10-04 | Magnetomechanical coupling and ferromagnetic resonance in magnetic nanoparticles | We address the theory of the coupled lattice and magnetization dynamics of
freely suspended single-domain nanoparticles. Magnetic anisotropy generates
low-frequency satellite peaks in the microwave absorption spectrum and a
blueshift of the ferromagnetic resonance (FMR) frequency. The low-frequency
resonances are very ... | 1610.01072v2 |
2016-10-05 | Finite-dimensional colored fluctuation-dissipation theorem for spin systems | When nano-magnets are coupled to random external sources, their magnetization
becomes a random variable, whose properties are defined by an induced
probability density, that can be reconstructed from its moments, using the
Langevin equation, for mapping the noise to the dynamical degrees of freedom.
When the spin dynam... | 1610.01622v1 |
2017-03-31 | Spin Seebeck effect in Y-type hexagonal ferrite thin films | Spin Seebeck effect (SSE) has been investigated in thin films of two
Y-hexagonal ferrites Ba$_2$Zn$_{2}$Fe$_{12}$O$_{22}$ (Zn2Y) and
Ba$_2$Co$_{2}$Fe$_{12}$O$_{22}$ (Co2Y) deposited by a spin-coating method on
SrTiO$_3$(111) substrate. The selected hexagonal ferrites are both
ferrimagnetic with similar magnetic moments... | 1703.10903v1 |
2017-06-02 | Power Loss for a Periodically Driven Ferromagnetic Nanoparticle in a Viscous Fluid: the Finite Anisotropy Aspects | The joint magnetic and mechanical motion of a ferromagnetic nanoparticle in a
viscous fluid is considered within the dynamical approach. The equation based
on the total momentum conservation law is used for the description of the
mechanical rotation, while the modified Landau-Lifshitz-Gilbert equation is
utilized for t... | 1706.00777v2 |
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