Orbital moment probed spin orbit coupling effects on anisotropy and damping in CoFeB thin films

Abstract

A strong correlation between coercivity, in-plane uniaxial magnetic anisotropy (UMA) and Gilbert damping constant in technologically important CoFeB thin films is demonstrated on the basis of static and dynamic magnetization measurements through compositional and stress variations. A large UMA is induced in CoFeB films over a wide range of Fe/Co ratios as a consequence of oblique co-sputtering from Co₂₀Fe₆₀B₂₀ and Co targets. The UMA and damping variations are consistent with the calculated Landé g-factor, whose asymmetry gives rise to UMA and anisotropic damping via spin orbit coupling. The study highlights the fabrication of films having reasonable anisotropy with tailored damping properties.