Highly fcc-textured Pt–Al alloy films grown on MgO(001) showing enhanced spin Hall efficiency

Abstract

We report on a systematic comparative study of the spin Hall efficiency between highly face-centered cubic (fcc)-textured Pt–Al alloy films grown on MgO(001) and poorly crystallized Pt–Al alloy films grown on SiO2. Using CoFeB as the detector, we show that for Al compositions centering around x = 25, mainly L12-ordered Pt100−xAlx alloy films grown on MgO exhibit outstanding charge-spin conversion efficiency. For the Pt78Al22/CoFeB bilayer on MgO, we obtain damping-like spin Hall efficiency as high as ξDL ∼ +0.20 and expect up to a sevenfold reduction in power consumption compared to the polycrystalline bilayer of the same Al composition on SiO2. This work demonstrates that improving the crystallinity of fcc Pt-based alloys is a crucial step for achieving large spin Hall efficiency and low power consumption in this material class.