Controllable magnetization precession dynamics and damping anisotropy in Co2FeAl Heusler-alloy films

Abstract

Magnetization dynamics of the epitaxially-grown Co₂FeAl (CFA) thin films have been systematically investigated by the time-resolved magneto-optical Kerr effect (TR-MOKE). The dependences of precession frequency f, relaxation time τ and magnetic damping factor α upon the orientation of applied magnetic field are found to have a strong four-fold symmetry. Two series of samples with various substrate temperatures (T_s) and thickness (t_CFA) were prepared and a large Gilbert damping difference between the hard and easy axes is extracted to be 3.3 × 10⁻³ after subtracting the extrinsic contributions of spin pumping, two-magnon scattering and magnetic inhomogeneities. The four-fold variation of Gilbert damping relates closely to the in-plane magnetocrystalline anisotropy and can be attributed to the anisotropic distribution of spin–orbit coupling. Our findings provide new insights into the anisotropic properties of magnetization and damping, which is very helpful for designing and optimizing advanced spintronic devices on different demands.