Current-induced perpendicular magnetization switching without external magnetic field in gate-induced asymmetric structure

Abstract

We demonstrate current-induced switching of perpendicular magnetization without any external magnetic field by introducing lateral structural asymmetry through gate-induced redox reactions. A gate electrode was fabricated to cover only half of a heavy metal/ferromagnet/oxide wire, allowing a gate voltage to form an in-plane oxidation gradient. The essential role of structural asymmetry is evidenced by the fact that external-field-free deterministic switching is absent when the gate electrode covers an entire wire. We confirm that the current-induced perpendicular effective field deterministically drives the magnetization direction at zero field. Magnetic domain imaging and transport measurements clarify that the origin of the perpendicular effective field is not the Rashba effect, but the Oersted field at the wire edges.