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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Book ChapterDOI
Recent Analytical Developments in Micromagnetics
TL;DR: In this article, the scaling law of the minimum energy in micromagnetics has been studied and two approaches based on asymptotic analysis have been proposed to solve the problem.
Journal ArticleDOI
Theory of synergy between electron cyclotron and lower hybrid waves
R. J. Dumont,G. Giruzzi +1 more
TL;DR: In this paper, a theoretical study of the improvement of the electron cyclotron current drive (ECCD) efficiency in regimes in which most of the current is driven by lower hybrid (LH) waves is presented.
Journal ArticleDOI
Thermally activated processes in magnetic systems consisting of rigid dipoles: equivalence of the Ito and Stratonovich stochastic calculus
D V Berkov,N L Gorn +1 more
TL;DR: In this article, it was shown that the Ito and Stratonovich stochastic calculus lead to identical results when applied to the stochastically dynamics study of magnetic systems consisting of dipoles with the constant magnitude, despite the multiplicative noise appearing in the corresponding Langevin equations.
Journal ArticleDOI
Magnetic field induced spin-wave energy focusing
Noel Perez,Luis Lopez-Diaz +1 more
TL;DR: In this paper, the same effect can be achieved by a reduction in the external field instead of a constriction at the edge and furthermore, both the location and the amount of energy to be delivered to the lattice can be controlled accurately this way.
Journal ArticleDOI
Detection of magnetic nanoparticles utilizing cooled normal pickup coil and high Tc SQUID
Keiji Enpuku,S. Nabekura,Y. Tsuji,S. Okada,Masaaki Matsuo,Akira Tsukamoto,Takako Mizoguchi,Akihiko Kandori +7 more
TL;DR: In this paper, a measurement system was developed to detect the position and amount of the magnetic nanoparticles accumulated inside the body by using a cooled Copper pickup coil and high T c SQUID.
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.