Enhancement of spin Hall effect in O-implanted Pt by side jump scattering

Materials exhibiting high damping-like spin-orbit torque efficiency, θ_DL owing to extrinsic spin Hall effect (SHE) are of interest in magnetization switching, auto oscillations, and domain wall motion. However, the value of θ_DL for heavy metals such as Pt is ∼0.06 [1]. Recent studies have shown enhancement in θ_DL by incorporating non-metallic elements in Pt such as S, N [2,3] but incorporation of these elements by sputtering [3] have shown non-monotonic θ_DL with varying concentrations. Here, we report a high θ_DL in modified Pt, designed by non-metallic O ion implantation [4], at an optimized low energy of 20 keV with varying dose from 2 ×10¹⁶-1 ×10¹⁷ ions cm^-2. We achieved a 3.5 times monotonic increase in θ​​​​​​​_DL from 0.064 to 0.230 with a smaller trade-off in resistivity, ρ_xx from 55.4 to 159.5 µΩ cm. We find that the spin Hall resistivity, ρ_SH, is proportional to the square of resistivity from impurities, ρ_imp, i.e., ρ_SH ∝ (ρ_imp)², indicating an extrinsic SHE mechanism of side jump scattering as the dominant origin of enhanced θ​​​​​​​_DL. These results encourage implantation-engineering as an effective tool to design materials for developing the next-generation devices that can exert high θ_DL for low energy manipulation of magnetization, indispensable in spintronics field.