Langevin micromagnetics of recording media using subgrain discretization

Finite element based micromagnetics is applied to study thermally assisted switching of thin film media in the high speed regime. The space discretization leads to a system of stochastic differential equations with multiplicative noise which is interpreted in the sense of Stratonovich and solved using the method of Heun. For a CoCrPt alloy system, an external field of -255 kA/m was found to be sufficient to switch the magnetization in less than 1 ns in about 80% of the realizations of the stochastic process. However reversal times up to 1 ns and higher are observed for about 20% of the calculations. Then the system switches from the high remanent state to a metastable state where it remains trapped for several nanoseconds.