Micromagnetic study of fieldlike spin torque effect on the magnetization switching in tunnel junctions with perpendicular anisotropy

Micromagnetic simulation is employed to study the effect of fieldlike spin torque in a perpendicularly magnetized tunnel junction. We find that the effect of fieldlike spin torque strongly depends on the current direction, showing the torque significantly reduces the switching time for the electrons flowing from free layer to pinned layer while has less effect for the opposite current. This asymmetric behavior is consistent with the theoretical prediction on the bias dependence of the fieldlike spin torque. The observed absence of preswitching and postswitching oscillations can be attributed to the opposite precession phase of local magnetic moments within the free layer.