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 θSH 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 both effective spin Hall angle and spin Hall conductivity degraded with lowering the growth temperature to 300 °C due to degradation of the interfacial spin transparency, they were recovered by reducing the sputtering Ar gas pressure. We achieved a giant θSH up to 7.8 and demonstrated efficient spin–orbit torque magnetization switching by ultralow current density of ∼105 A/cm2 in YPtBi grown at 300 °C with the Ar gas pressure of 1 Pa. Our results provide the recipe to achieve giant θSH in YPtBi grown at lower growth temperature suitable for BEOL process.