Micromagnetic simulation on effect of oersted field and hard axis field in spin transfer torque switching

The effects of the current-induced Oersted field and of a hard axis applied field on spin transfer torque (STT) switching have been investigated by performing LLG micromagnetic simulations including a STT term and Gaussian thermal fluctuations. In parallel to anti-parallel switching at large currents, the C-like micromagnetic configuration induced by the Oersted field plays an important role in STT switching. In anti-parallel to parallel switching at large currents, the Oersted field induces a complicated micromagnetic configuration with several vortices. In both cases, the magnetization deviates considerably from macrospin behaviour. However, a macrospin-like behaviour is restored when a hard axis field is present.