Comparative study on the origin of spin Hall effect in poly and single crystalline α-W in W/CoFeB bilayers

In this work we have aimed to deposit polycrystalline and epitaxial α-W films and estimate the spin Hall angle (SHA) of the above-mentioned phases of W. We have employed spin-torque ferromagnetic resonance (ST-FMR) technique to understand the origin of spin Hall effect (SHE) in polycrystalline α-W and compare it with the epitaxially grown α-W in W/CFB bilayers. We have observed that the polycrystalline film of α-W has shown contributions from both extrinsic and intrinsic origins of SHE while the epitaxial film of α-W has majorly shown contributions from intrinsic origin of SHE.