Highly dose dependent damping-like spin‒orbit torque efficiency in O-implanted Pt

Abstract

Damping-like torque (DLT) arising from the spin Hall effect (SHE) in heavy metals and their alloys has been widely explored for applications in spin–orbit torque MRAM, auto-oscillations, spin waves, and domain wall motion. In conventional materials, the DLT efficiency is limited by intrinsic properties, while attaining strong spin–orbit coupling and higher spin-charge interconversion, with no compromise to electric properties, is the need of the hour. In this Letter, we report more than 3.5 times increase in DLT efficiency, θDL, of modified Pt-oxide by employing a better approach of low energy 20 keV O+ ion implantation. The highest fluence of O+ implantation (1 × 1017 ions cm−2) in Pt enhanced the DLT efficiency from 0.064 to 0.230 and improved the spin transmission for a smaller trade-off in the longitudinal resistivity (𝜌Pt to 𝜌Pt−Oxide) from 55.4 to 159.5 μΩ cm, respectively. The transverse spin Hall resistivity, 𝜌SH, is found to be proportional to the square of the longitudinal resistivity, i.e., 𝜌impSH∝𝜌2imp, implying that the enhanced SHE in O-implanted Pt is due to a side-jumping mechanism. Further, no break in the twofold as well as mirror symmetry of torques from the O-implanted Pt allows the use of spin-torque ferromagnetic resonance-based line shape analysis to quantify such torques.