Intrinsic spin Hall effect in oxidized platinum/magnetic oxide heterostructure

Abstract

Oxidizing the heavy metal (HM) has been reported to be a simple and efficient method to enhance the generation efficiency of the spin–orbit torques (SOTs) in the HM/ferromagnet (FM) heterostructure, which has attracted intensive studies. However, by now all the previous studies were performed using an oxidized HM/metallic magnet heterostructure. The SOT in the oxidized HM/magnetic oxide heterostructure still remains elusive, which has not been reported yet. In this work, we report the study of the SOT generation and spin Hall effect in the oxidized platinum/magnetic oxide heterostructure. By changing the oxidation level of Pt(O) in the Pt(O)/Tm3Fe5O12 (TmIG) bilayer, we demonstrate that the SOT efficiency drastically decreases with the increase in the oxidation level, which is completely opposite to that in the Pt(O)/metallic magnet. This result indicates that the interfacial oxidation of the FM layer in the generally studied oxidized HM/metallic magnet bilayer significantly contributes to the interfacial Rashba effect, which drastically enhances the SOT efficiency. We further demonstrate that the spin Hall conductivity of Pt is very sensitive to the electric conductivity, which drastically increases with the electric conductivity. This drastic increase is attributed to the intrinsic contribution of Pt in the dirty-metal regime, which is dominated by the carrier lifetime. Our study provides a piece of information for the basic understanding of the SOT and spin Hall effect in the oxidized HM/magnetic oxide heterostructure.