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.

The spin–orbit torques within a Pt/Tm₃Fe₅O₁₂ (TmIG) bilayer offer an expedient method for manipulating the magnetization of TmIG. However, the practical application of TmIG is hindered by the presence of an external field during switching. Here, we demonstrate field-free magnetization switching in Pt/TmIG bilayer on a vicinal substrate with minimal sacrifice to the perpendicular magnetic anisotropy (PMA) of TmIG. With the assistance of tilt PMA, reversible perpendicular magnetization switching is realized in the absence of an external field. Our results offer an alternative solution for achieving field-free perpendicular magnetization switching in a Pt/TmIG bilayer, thereby fostering the advancement of emerging SOT-based devices.

Electrical spin-orbit torque (SOT) in magnetic insulators (MI) has been intensively studied due to its advantages in spin-orbitronic devices with ultralow energy consumption. However, the magnon torque in the MIs, which has the potential to further lower the energy consumption, still remains elusive. In this work, we demonstrate the efficient magnon torque transferred into an MI through an antiferromagnetic insulator. By fabricating a Pt/NiO/Tm${}_3$Fe${}_5$O${}_{12}$ heterostructure with different NiO thicknesses, we have systematically investigated the evolution of the transferred magnon torque. We show that the magnon torque efficiency transferred through the NiO into the MI can retain a high value (∼50%), which is comparable to the previous report for the magnon torque transferred into the metallic magnet. Our study manifests the feasibility of realizing the pure magnon-based spin-orbitronic devices with ultralow energy consumption and high efficiency.

Studying the mechanisms of the spin Hall effect (SHE) is essential for the fundamental understanding of spintronic physics. By now, despite the intensive studies of SHE on heavy metal (HM)/metallic magnet heterostructures, the SHE on HM/ferrimagnetic insulator (FMI) heterostructures still remains elusive. Here, we study the mechanism of SHE in the Pt/Tm${}_3$Fe${}_5$O${}_{12}$ (TmIG) heterostructure. We first tune the crystallinity and resistivity of Pt by an annealing method, and then study the spin–orbit torque (SOT) in the tuned-Pt/TmIG devices. The SOT generation efficiency per unit electric field and spin Hall angle were obtained, which are insensitive to the annealing temperature. We further demonstrate that the intrinsic contribution in the moderately dirty regime is responsible for the SHE in our Pt/TmIG bilayer. Our study provides an important piece of information for the SHE in FMI-based spintronic physics.