Dependence of sub-volume excitation on structural and material parameters in precessional regime of spin transfer torque magnetization reversal

We studied the structural and material parameter dependence of sub-volume excitation in a precessional regime of spin transfer torque (STT) magnetization reversal for CoFeB/MgO-based p-magnetic tunnel junctions (MTJs) using LLG micromagnetic simulation. The current density dependence of swiT_Ching and incubation time in STT magnetization reversal can be globally scaled by the macrospin theory regardless of sub-volume excitation. The transit time has the minimum value at the minimum MTJ diameter where the sub-volume is excited. This critical diameter increases with an increase in exchange stiffness. The mechanism that sub-volume excitation is related to current density is also discussed.