SOT induced magnetization reversal in Pt/[Co/Ni]2/Co/Ta multilayer Hall bars without external magnetic field

Summary form only given. In this work, we show that by selecting PMA material with a weak out-of-plane anisotropy, SOT-induced magnetization reversal can be achieved without the assistance of external magnetic field. Our material stacks comprise of Pt/[Co/Ni]n/Co/Ta, where n = 2, 3 and 4. The magnetization switching is observed by the Hall resistance change with an in-plane DC current flow in the structure with n = 2. The measured R
_H
as a function of the DC current. A clear hysteresis loop was obtained, implying a deterministic switching of the magnetization induced by the applied current. Firstly the magnetization is aligned along the +z orientation. No change in R
_H
is observed when positive current (along +x direction) flows through the wire. As the current is swept in the opposite direction, negative current (along -x direction), RH exhibits a step wise decrease at a current of -4 mA, reaching saturation at -6.5 mA. This implies that the magnetization has switched to the -z orientation. As the current is then increased towards +6.5 mA, the initial change in RH signal occurs at 2 mA, with a quasi-stable state at +3 mA and saturation at +4 mA. This results in an asymmetric hysteresis loop.