Damping and spin mixing conductance in Ni80Fe20/CuIr structures: effect of Ir doping

Abstract

Ni80Fe20(Py) thin films of different thicknesses have been sputtered on thermally oxidized Si substrates and capped with Pt or Cu doped with , and of Ir. Vibrating sample magnetometery has been used to measure the magnetization at saturation. Microstrip line ferromagnetic resonance (MS-FMR) has been used to investigate the Py and capping layer thickness dependence of the damping parameter enhancement due to the spin pumping. The experimental data have been analyzed using a model for spin pumping that includes the effective spin mixing conductance at the Py/HM (HM = Pt and CuIr) interface and the spin-diffusion length of HM. The spin mixing conductance (spin diffusion length) increases (decreases) as Ir doping increases. For samples capped with Pt (CuIr(6%)), the obtained values of spin mixing conductance and the spin diffusion length have been estimated to be 25 nm−2 (9.87 nm−2) and 1.05 nm (2.8 nm), respectively. MS-FMR measurements revealed that the effective magnetization varies linearly with the effective Py thickness due to the perpendicular surface anisotropy.