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

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 frequencyf, relaxation timeτand magnetic damping factorαupon 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 × 10⁻³after 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.