Journal ArticleDOI
Langevin-dynamics study of the dynamical properties of small magnetic particles
TLDR
In this paper, the Langevin-dynamics approach was used to study the dynamics of magnetic nanoparticles, and the results were compared with different analytical expressions used to model the relaxation of nanoparticle ensembles, assessing their accuracy.Abstract:
The stochastic Landau-Lifshitz-Gilbert equation of motion for a classical magnetic moment is numerically solved (properly observing the customary interpretation of it as a Stratonovich stochastic differential equation), in order to study the dynamics of magnetic nanoparticles. The corresponding Langevin-dynamics approach allows for the study of the fluctuating trajectories of individual magnetic moments, where we have encountered remarkable phenomena in the overbarrier rotation process, such as crossing-back or multiple crossing of the potential barrier, rooted in the gyromagnetic nature of the system. Concerning averaged quantities, we study the linear dynamic response of the archetypal ensemble of noninteracting classical magnetic moments with axially symmetric magnetic anisotropy. The results are compared with different analytical expressions used to model the relaxation of nanoparticle ensembles, assessing their accuracy. It has been found that, among a number of heuristic expressions for the linear dynamic susceptibility, only the simple formula proposed by Shliomis and Stepanov matches the coarse features of the susceptibility reasonably. By comparing the numerical results with the asymptotic formula of Storonkin {Sov. Phys. Crystallogr. 30, 489 (1985) [Kristallografiya 30, 841 (1985)]}, the effects of the intra-potential-well relaxation modes on the low-temperature longitudinal dynamic response have been assessed, showing their relatively small reflection in the susceptibility curves but their dramatic influence on the phase shifts. Comparison of the numerical results with the exact zero-damping expression for the transverse susceptibility by Garanin, Ishchenko, and Panina {Theor. Math. Phys. (USSR) 82, 169 (1990) [Teor. Mat. Fiz. 82, 242 (1990)]}, reveals a sizable contribution of the spread of the precession frequencies of the magnetic moment in the anisotropy field to the dynamic response at intermediate-to-high temperatures.read more
Citations
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Journal ArticleDOI
Spin-Transfer Torque Magnetization Reversal in Uniaxial Nanomagnets with Thermal Noise
TL;DR: In this article, the authors consider the thermally assisted, low spin-torque, switching asymptotics of a thin-film uniaxial magnet subject to spintorque effects and thermal fluctuations (thermal noise) and present analytical results for the mean switching time behavior.
Journal ArticleDOI
An Asynchronous and Low-Power True Random Number Generator Using STT-MTJ
Ben Perach,Shahar Kvatinsky +1 more
TL;DR: The asynchronous design enables the decoupling of the random number generation from the system clock, allowing it to be embedded in low-power devices and achieving an entropy generating rate between 99.7 and 127.7 pJ per bit for 90% of the instances.
Journal ArticleDOI
All-Optical Helicity-Dependent Switching in Hybrid Metal–Ferromagnet Thin Films
Feng Cheng,Zhidong Du,Xinjun Wang,Ziqiang Cai,Lin Li,Chuangtang Wang,Abdelkrim Benabbas,Paul M. Champion,Nian X. Sun,Liang Pan,Yongmin Liu +10 more
TL;DR: In this article, all-optical helicity-dependent switching (AO-HDS) in hybrid metal-ferromagnet thin films, which consist of Co/Pt multilayers with perpendicular magnetic anisotropy and an Au film capping layer on the top, is experimentally demonstrated.
Journal ArticleDOI
Hidden symmetries and equilibrium properties of multiplicative white-noise stochastic processes
TL;DR: In this article, the authors define the time reversal transformation for Markovian multiplicative white-noise processes, taking into account that the asymptotic stationary probability distribution depends on the prescription.
Journal ArticleDOI
The effect of Neel relaxation on the properties of the third harmonic signal of magnetic nanoparticles for use in narrow-band magnetic nanoparticle imaging
TL;DR: In this article, the authors measured the properties of the third harmonic signal of magnetic nanoparticles, such as frequency and magnetic field dependencies, when the behavior of MNPs was dominated by Neel relaxation.
References
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Journal ArticleDOI
Handbook of Mathematical Functions
Book
Stochastic processes in physics and chemistry
TL;DR: In this article, the authors introduce the Fokker-planck equation, the Langevin approach, and the diffusion type of the master equation, as well as the statistics of jump events.
Stochastic Processes in Physics and Chemistry
Abstract: Preface to the first edition. Preface to the second edition. Abbreviated references. I. Stochastic variables. II. Random events. III. Stochastic processes. IV. Markov processes. V. The master equation. VI. One-step processes. VII. Chemical reactions. VIII. The Fokker-Planck equation. IX. The Langevin approach. X. The expansion of the master equation. XI. The diffusion type. XII. First-passage problems. XIII. Unstable systems. XIV. Fluctuations in continuous systems. XV. The statistics of jump events. XVI. Stochastic differential equations. XVII. Stochastic behavior of quantum systems.
Book
Numerical Solution of Stochastic Differential Equations
Peter E. Kloeden,Eckhard Platen +1 more
TL;DR: In this article, a time-discrete approximation of deterministic Differential Equations is proposed for the stochastic calculus, based on Strong Taylor Expansions and Strong Taylor Approximations.