Dresden 2014 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 29: Magnetization Dynamics II

MA 29.12: Vortrag

Mittwoch, 2. April 2014, 18:00–18:15, HSZ 401

ON THE KRAMERS VERY LOW DAMPING ESCAPE RATE FOR POINT PARTICLES AND CLASSICAL SPINS — •William T. Coffey¹, William J. Dowling², Yuri P. Kalmykov³, and Serguey V. Titov⁴ — ¹Department of Electronic and Electrical Engineering, Trinity College, Dublin 2, Ireland — ²Department of Electronic and Electrical Engineering, Trinity College, Dublin 2, Ireland — ³University of Perpignan, Perpignan, France — ⁴Kotelnikov Institute of Radio Engineering and Electronics, RAS, Russia

The seminal Kramers result for the very low dissipation (VLD) escape rate of point particles from a potential well is rigorously derived by writing following Stratonovich, the Langevin equation (LE) in energy (slow) and configuration (fast) variables which now contain a multiplicative noise term. The corresponding Fokker-Planck equation (FPE) in configuration-energy space may then be written via the Kramers-Moyal expansion merely by calculating the drift and diffusion coefficients from the LE given the Stratonovich interpretation. The configuration-energy LE method may be transparently generalized following transformations given very recently by Dunn et al. [T. Dunn et al., in Fluctuating Nonlinear Oscillators, Ed. by M.I. Dykman, Oxford University Press, Oxford, 2012], to the stochastic motion of classical spins executing Stoner-Wohlfarth orbits in nonaxially symmetric anisotropy-Zeeman potentials which is governed by the Landau-Lifshitz-Gilbert equation yielding an exact expression for the VLD mean first passage time whence the Kramers VLD rate for spins.