Giant spin Hall effect in half-Heusler alloy topological semimetal YPtBi grown at low temperature

Abstract

Half-Heusler alloy topological semimetal YPtBi is a promising candidate for an efficient spin source material having both large spin Hall angle $θ$$_{SH}$ and high thermal stability. However, high-quality YPtBi thin films with low bulk carrier density are usually grown at 600$°$C, which exceeds the limitation of 400$°$C for back end of line (BEOL) process. Here, we investigate the crystallinity and spin Hall effect of YPtBi thin films grown at lower growth temperature down to 300$°$C. Although $θ$$_{SH}$ degraded with lowering the growth temperature to 300$°$C due to degradation of the crystallinity, it was recovered by reducing the sputtering Ar gas pressure. We achieved a giant $θ$$_{SH}$ up to 8.2 and demonstrated efficient spin-orbit torque magnetization switching by ultralow current density of ~10$^5$ A/cm$^2$ in YPtBi grown at 300$°$C with the Ar gas pressure of 1 Pa. Our results provide the recipe to achieve giant $θ$$_{SH}$ in YPtBi grown at lower growth temperature suitable for BEOL process.