Regensburg 2019 – wissenschaftliches Programm
DY 21.2: Vortrag
Dienstag, 2. April 2019, 14:15–14:30, H6
On the derivation of the escape rate of giant classical magnetic spins via an adaptation of the very low damping method of Kramers for particles — •Declan Byrne1, William Coffey1, Yuri Kalmykov2, and Serguey Titov3 — 1Department of Electronic and Electrical Engineering, Trinity College, Dublin 2, Ireland — 2Laboratoire de Mathématiques et Physique, Université de Perpignan Via Domitia, 54, Avenue Paul Alduy, F-66860 Perpignan, France — 3Kotel'nikov Institute of Radio Engineering and Electronics of the Russian Academy of Sciences, Vvedenskii Square 1, Fryazino, Moscow Region, 141190, Russian Federation
It is demonstrated how the original perturbative Kramers' method (starting from the phase space coordinates only) [H.A. Kramers, Physica 7, 384 (1940)] of determining the energy-controlled-diffusion equation for Newtonian particles with separable and additive Hamiltonians may be easily modified to yield the energy-controlled diffusion equation and thus the very low damping escape rate (including spin-transfer torque) for classical giant magnetic spins with two degrees of freedom. These have dynamics governed by the magnetic Langevin and Fokker-Planck equations and thus are generally based on non-separable and non-additive Hamiltonians. The derivation of the VLD rate directly from the (magnetic) Fokker-Planck equation in the space of polar angles of the magnetization following from the Kramers method is much simpler than those previously used which involve inter alia transformation to energy and phase variables as well as the properties of multiplicative noise.