Current-driven magnetization switching under zero field in Pt/Ta(wedge)/CoFeB/MgO multilayers

Abstract

The switching of perpendicularly magnetized ferromagnets via current-induced spin–orbit torques is of great interest because of its potential applications in memory and logic devices. However, the in-plane electric current itself is not enough to switch the magnetization. In addition to the electric current, an in-plane external magnetic field is required for magnetization switching. This limits the usage of such devices in spintronic applications. Here, we work on the current-driven perpendicular magnetization switching in the Pt/Ta(wedge)/CoFeB/MgO multilayer. The structural symmetry is broken in both z-axis and in-plane due to the wedge Ta layer, which results in a field-like spin–orbit torque. The [Formula: see text] value extracted from the slope of the offset field vs current density increases with Ta layer thickness (<1.0 nm) and then decreases up to <1.3 nm. Thanks to both in-plane and z-axis asymmetries that enable the current-driven magnetization switching without the need for a magnetic field. We showed switching of the magnetization with a perpendicular magnetic anisotropy, switching in a wide range of Ta layer in Pt/Ta(wedge)/CoFeB/MgO multilayer.