RT Journal Article
T1 Monte Carlo technique with a quantified time step: Application to the motion of magnetic moments
A1 Chubykalo-Fesenko, Oksana
A1 Nowak, Ulrich
A1 Smirnov Rueda, Román
A1 Wongsam, Michael Anthony
A1 Chantrell, Roy
A1 González, M. J.
AB The viability of the time quantified Metropolis Monte Carlo technique to describe the dynamics of magnetic systems is discussed. Similar to standard Brownian motion, the method is introduced basing on the comparison between the Monte Carlo trial step and the mean squared deviation of the direction of the magnetic moment. The Brownian dynamics approach to the time evolution of a magnetic moment is investigated and expressions for the mean square deviations are obtained. However, the principle difference between the standard Brownian motion and the magnetic moments dynamics is the presence of the spin precession which constitutes the reversible part of the dynamics. Although some part of the precession contributes to the diffusion coefficient, it also gives rise to athermal, energy conserving motion which cannot be taken into account by Monte Carlo methods. It is found that the stochastic motion of a magnetic moment falls into one of two possible regimes: (i) precession dominated motion, (ii) nonprecessional motion, according to the value of the damping constant and anisotropy strength and orientation. Simple expressions for the diffusion coefficient can be obtained in both cases for diffusion dominated motion, i.e., where the athermal precessional contribution can be neglected. These simple expressions are used to convert the Monte Carlo steps to real time units. The switching time for magnetic particles obtained by the Monte Carlo with time quantification is compared with the numerical integration of the Landau-Lifshitz-Gilbert equations with thermal field contribution and with some well known asymptotic formulas.
PB American Physical Society
SN 1098-0121
YR 2003
FD 2003-02-01
LK https://hdl.handle.net/20.500.14352/50489
UL https://hdl.handle.net/20.500.14352/50489
LA eng
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NO O.C. acknowledges the hospitality and support fromDurham University, U.K., Duisburg University, Germany,and Seagate Research Center, Pittsburgh, where a part of this work was done. R.S.-R. thanks Durham University, U.K., for hospitality and support. M.A.W. thanks ICMM, Madrid,Spain for hospitality and support, and acknowledges the EPSRC who supported this project under Grant No.R040 318.
NO EPSRC
DS Docta Complutense
RD 30 abr 2024