Stability of magnetization states in a ferromagnet/heavy metal bilayer structure

Abstract

The influence of spin Hall effect on magnetization dynamics is one of the hottest topics in spintronics. In this paper, the magnetization dynamics driven by the spin Hall effect-induced torque in a ferromagnet /heavy metal bilayer structure has been investigated theoretically. By linearizing the Landau-Lifshitz-Gilbert equation which includes the spin Hall effect torque term, and taking stability analysis, the phase diagrams in the plane defined by the current density and external magnetic field have been obtained. Under the control of the current density and external magnetic field, several magnetic states, such as in-plane stable state, in-plane precession and bistable states can be realized. With the external magnetic field oriented within a certain range, the magnetization reversal and precession can be realized through adjusting the current density. In addition, the dynamic evolutions of these magnetic states are demonstrated by solving the temporal evolutive equations numerically.