Magnetic damping constant of Co2FeSi Heusler alloy thin film

${\mathrm{Co}}_2\mathrm{Fe}\mathrm{Si}$ films were prepared using magnetron sputtering technique on Cr buffer layers and MgO(001) substrates at various annealing temperatures. We investigated the crystal structures, magnetic properties ($M_s$ and $H_c$ ), surface roughness, and magnetic damping constants $\left(\alpha \right)$ of the prepared ${\mathrm{Co}}_2\mathrm{Fe}\mathrm{Si}$ films. Out-of-plane angular dependences of the resonance field and the linewidth of the ferromagnetic resonance spectra were measured and fitted using the Landau-Lifshitz-Gilbert equation to determine the damping constant. The as-deposited ${\mathrm{Co}}_2\mathrm{Fe}\mathrm{Si}$ film exhibited an amorphous and disordered structure; the $\alpha$ value was 0.008. In contrast, the ${\mathrm{Co}}_2\mathrm{Fe}\mathrm{Si}$ films annealed over $300°\mathrm{C}$ showed epitaxial growth and had a (001)-oriented and $L{2}_1$ ordered structure. Both disordered and $L{2}_1$ ordered ${\mathrm{Co}}_2\mathrm{Fe}\mathrm{Si}$ films showed similar $\alpha$ values.