Spin pumping and spin torques in interfacially tailored Co2FeAl/β -Ta layers

Abstract

The Heusler ferromagnetic (FM) compound $\mathrm{C}{\mathrm{o}}_{2}\mathrm{FeAl}$ interfaced with a high spin-orbit coupling nonmagnetic (NM) layer is a promising candidate for energy-efficient spin-logic circuits. The circuit potential depends on the strength of angular momentum transfer across the FM/NM interface, hence requiring low spin-memory loss and high spin-mixing conductance. To highlight this issue, spin pumping and spin torque ferromagnetic resonance measurements have been performed on $\mathrm{C}{\mathrm{o}}_{2}\mathrm{FeAl}/\ensuremath{\beta}$-Ta heterostructures tailored with Cu interfacial layers. The interface tailored structure yields an enhancement of the effective spin-mixing conductance. The interface transparency and spin-memory loss corrected values of the spin-mixing conductance, spin Hall angle, and spin-diffusion length are found to be $3.40\ifmmode\pm\else\textpm\fi{}0.01\ifmmode\times\else\texttimes\fi{}{10}^{19}\phantom{\rule{4pt}{0ex}}{\mathrm{m}}^{\ensuremath{-}2}$, $0.029\ifmmode\pm\else\textpm\fi{}0.003$, and $2.3\ifmmode\pm\else\textpm\fi{}0.5\phantom{\rule{4pt}{0ex}}\mathrm{nm}$, respectively. Furthermore, a high current modulation of the effective damping of around $2.1%$ has been achieved at an applied current density of $1\ifmmode\times\else\texttimes\fi{}{10}^{9}\mathrm{A}/{\mathrm{m}}^{2}$, which clearly indicates the potential of using this heterostructure for energy-efficient control in spin devices.