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
Micromagnetic Analysis of Thermal Magnetization Fluctuations in Ferromagnetic Nanowires
Journal ArticleDOI
Atomistic Theory of Thermally Activated Magnetization Processes in Nd<sub>2</sub>Fe<sub>14</sub>B Permanent Magnet
TL;DR: In this paper , an atomistic Hamiltonian was proposed for the Nd2Fe14B magnet and various thermodynamic properties, e.g., the temperature dependence of the magnetization showing a spin reorientation transition, magnetic anisotropy energy, the domain wall profiles, the anisotropic of the exchange stiffness constant, and the spectrum of ferromagnetic resonance.
Posted Content
Thermally excited spin waves in a nano-structure: thermal gradient vs. constant temperature
TL;DR: In this paper, the effects of a uniform temperature and a uniform thermal gradient on spin dynamics in micromagnetic simulations have been investigated, showing that the stochastic field leads to an increase of the precession angle of the magnetization, and a mild decreas of the linewidth of the resonance peaks.
Posted Content
Band-pass Magnetic Tunnel Junction based Magnetoresistive Random Access Memory
TL;DR: In this paper, the spin transfer torque (STT-MRAM) was proposed to improve the energy efficiency of a traditional trilayer MRAM by employing the Green's function spin transport formalism coupled selfconsistently with the stochastic Landau-Lifshitz-Gilbert-Slonczewski equation.
Journal ArticleDOI
Interlayer Exchange Coupled Based Nanomagnetic Multiplier Architecture Design Methodology
TL;DR: In this paper, the reliability of the IEC-based multiplier model was determined by analyzing the temperature variation impact up to the Curie temperature, and it was noticed that unlike the dipole coupled architecture, the multiplier model has the capability of operating even up to Curie temperatures at sub-50nm justifying stability with respect to the temperature variations.
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.