Giant spin-torque generation by heavily oxidized Pt

We report a giant spin-torque generation originated from the ferromagnet/heavily oxidized Pt interface. The heavily oxidized Pt was fabricated by magnetron sputtering in a mixture of oxygen and argon gases with different oxygen flow rate Q from 50% to 100%. The dominant structure of the oxidized Pt is confirmed to be PtO2 in this Q range. We show that even in this heavily oxidized range, robust dampinglike and fieldlike spin torques can still be generated from the Ni81Fe19/oxidized Pt interface. By increasing the oxidation level of the oxidized Pt, the generation efficiencies of both dampinglike and fieldlike torques increase drastically, and noticeably, a maximum generation efficiency of 0.92 for the dampinglike torque is obtained. Our study further demonstrates that the generation efficiency of the dampinglike torque has a much larger value than that of the fieldlike torque, which indicates a dominant generation of the dampinglike torque from the interface. Since no energy dissipation occurs in the bulk of the spin-torque generator, this study provides a piece of information for the development of the energy-efficient spin-orbit devices based on insulating metallic oxides.