Modulated spin orbit torque via controlling the oxidation level of Ti in Pt/Co/TiOx heterostructures

We have investigated the oxidation effect on the spin orbit torque (SOT) in Pt/Co/TiOx heterostructures through controlling the oxidation time of Ti. The SOT induced magnetization switching in Pt/Co/Ti heterostructures is weak. However, it becomes evident as the oxidation of the Ti layer goes above a threshold level, and the magnetization can be completely switched when the oxidation time of the Ti layer is 11 min. With excessive oxidation, the SOT in the Pt/Co/TiOx films finally disappears. The average valence of the Ti was confirmed by X-ray photoelectron spectroscopy (XPS) spectra, which is about +3.619 for 11 min oxidation and the Ti2O3 will enhance the SOT efficiency. It is proposed that the oxidation will modulate the interfacial Rashba effect, the film qualities and the spin transparency at the interfaces, which will collectively dominate the SOT results.