Switching speed distribution of spin-torque-induced magnetic reversal

The switching probability of a single-domain ferromagnet under spin-current excitation is evaluated using the Fokker-Planck equation (FPE). In the case of uniaxial anisotropy, the FPE reduces to an ordinary differential equation in which the lowest eigenvalue λ1 determines the slowest switching events. We have calculated λ1 using both analytical and numerical methods. It is found that the previous model based on thermally distributed initial magnetization states [J. Z. Sun, Proc. SPIE 5359, 445 (2004)] can be accurately justified in some useful limiting conditions.