Anisotropic magnetic damping studies in β-Ta/2D-epitaxial-Py bilayers

We report on the anisotropy of the effective damping (alpha(eff)) in the sputtered beta-Ta(6 nm)/2D-epitaxial-Py (t(Py) = 3-10 nm) bilayers. In-plane field orientation dependent FMR measurements revealed a prominent anisotropy in alpha(eff), which is ascribed to the spin wave induced spin pumping from Py to beta-Ta in beta-Ta/epi-Py system. The results especially suggest that at lower t(Py) a relatively larger alpha(eff) and its anisotropic nature are present in beta-Ta/epi-Py bilayers as compared to bare epi-Py, which are unlikely at higher t(Py). This is possibly due to both spin pumping which stems from in-plane spin waves associated with two magnon scattering mechanism and interface induced anisotropy from heavy metals like beta-Ta at beta-Ta/Py interface. The in-plane H-r vs. phi reveals clear anisotropy behavior at t(Py) <= 4 nm. (C) 2017 Elsevier B.V. All rights reserved.