Giant Spin Hall Effect in Magnetron sputtered W₃Ta thin films

The spin Hall effect (SHE), in non-magnetic (NM) metals with strong spin-orbit coupling (SOC) has received much attention due to potential technological applications like magnetic random-access memory (MRAM) and spin-logic devices. Large spin Hall angles (SHA, the ratio of J_s/J_c) have been observed in materials like Pt and β-W (a.k.a. W₃W in the A15-structure), particularly when doped with oxygen reaching a peak value of 0.45. Recently, W₃Ta (and other A15 compounds) was theoretically predicted to host an even larger intrinsic SHE than β-W, originating from the large spin Berry curvature of its electronic band structure. Here we present experimental results on magnetron sputtered W₃Ta thin films, fabricated in Hall bar geometries using standard lithography and deposition techniques. The SHA was measured using ST-FMR on films of various thicknesses. Also, SHAs of various W_4-xTa_x compositions will be presented and compared with theoretical predictions.