Nonexponential magnetization thermal decay of a single-domain particle: Numerical computations using the dynamic Fokker-Planck equation

摘要

Nonexponential thermal decay of magnetization in a single-domain particle has been studied by numerically solving the Fokker-Planck equation as an initial value problem as well as an eigenvalue problem. The probability of not switching and switching time distribution is calculated for a wide range of applied fields and K_uV/k_BT values. In the low and intermediate energy barrier region, the switching time distribution is nonexponential. The switching time distribution is nonmonotonic and has one peak. For time less than the peak time, the distribution can be well fitted with inverse Gauss distribution; for time longer than the peak time, the distribution is exponential. The time constant of the exponential decay is equal to the inverse of the smallest eigenvalue of the Fokker-Planck equation. Furthermore, the switching time at the peak location of the distribution is a logarithmic function of the smallest eigenvalue.