Deterministic Spin–Orbit Torque Switching of a Perpendicularly Polarized Magnet Using Wedge Shape of the Magnet

Abstract

Spin–orbit torque provides an efficient way to switch magnets for low power memory applications by reducing the current density needed to switch the magnetization. Perpendicularly polarized magnets are preferred for high density data storage applications because of their high thermal stability in scaled dimensions. However, spin–orbit torque cannot switch a perpendicularly polarized magnet deterministically from up to down and down to up in the absence of an external magnetic field because spin–orbit torque alone cannot break the symmetry of the system. This poses a severe challenge to the applicability of spin–orbit torque for memory devices. In this paper, we show through micromagnetic simulations that when spin–orbit torque is applied on a magnet with a wedge shape, the moments of the magnet are aligned in-plane. On removal of the spin–orbit torque the moments deterministically evolve to vertically upward or downward direction because the anisotropy axis of the magnet is tilted away from the vertical direction owing to the wedge shape of the magnet. Thus, spin–orbit torque driven deterministic switching of the magnet in the absence of an external magnetic field is possible.