Fokker-Planck方程式の数値解による単磁区粒子の磁化反転

概要

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The magnetization reversal of single-domain particles at finite temperatures is investigated by numerically solving the Fokker-Planck equation. The equation has singularity at two particular positions. For an axially symmetric system, the problem is surmounted by introducing a novel probability function. For a non-axially symmetric system, it is overcome by using the Cartesian coordinates at these points. The methods above are validated by calculating frequency prefactors and comparing them with those from approximate analytic formulas. For the axially symmetric system, the dependence of the switching time on parameters such as the applied field, the temperature, and the volume is expressed as an experimental formula. For the non-axially symmetric case, assuming that the oblique angle of an applied field to the easy axis is a few degrees, the solution is expanded in a truncated Fourier series. The dependence of the switching time on the applied field and the damping constant is calculated. The effect of a gyromagnetic term in the equation on the switching time is also studied.
社団法人日本磁気学会の論文
2004-09-01