Strong Spin-Orbit Torque Induced by the Intrinsic Spin Hall Effect in Cr1-xPtx

We report on a spin-orbit-torque study of the spin-current generation in Cr1-xPtx alloy, using the light 3d ferromagnetic Co as the spin-current detector. We find that the dampinglike spin-orbit torque of Cr1-xPtx /Co bilayers can be enhanced by tuning the Cr concentration in the Cr1-xPtx layer, with a maximal value of 0.31 at the optimal composition of Cr0.2Pt0.8. The mechanism and the efficiency of spin-current generation in the Cr1-xPtx alloy can be fully understood by the characteristic trade-off between the intrinsic spin Hall conductivity of Pt and the spin carrier lifetime in the dirty limit. This suggests that Cr is simply as effective as other metals, oxides, and nitrides (e.g., Hf, Au, Pd, Cu, Ti, MgO, and Si3N4) in enhancing the dampinglike spin-orbit torque generated by the spin Hall effect of a Pt host via strengthening the spin carrier scattering and that alloying Pt with Cr does not employ observable spin-current generation via additional spin Hall effect, orbital Hall effect, or interfacial spin-orbit coupling effects. This work also establishes the low-resistivity Cr0.2Pt0.8 as an energy-efficient spin-orbit-torque provider for magnetic memory and computing technologies.

Automated summary

By studying the spin-orbit torque in Cr1-xPtx alloys, we have found that the dampinglike spin-orbit torque can be enhanced by tuning the Cr concentration in the Cr1-xPtx layer. The trade-off between the intrinsic spin Hall conductivity of Pt and the spin carrier lifetime in the dirty limit fully explains the mechanism and efficiency of spin-current generation in the Cr1-xPtx alloy.