Broad-Band FMR Linewidth of Co₂MnSi Thin Films with Low Damping Factor: The Role of Two-Magnon Scattering

The low Gilbert damping factor, which is usually measured by ferromagnetic resonance, is crucial in spintronic applications. Two-magnon scattering occurs when the orthogonality of the ferromagnetic resonance mode and other degenerate spin wave modes was broken by magnetic anisotropy, voids, second phase, surface defects, etc., which is important in analysis of ferromagnetic resonance linewidth. Direct fitting to linewidth with Gilbert damping is advisable only when the measured linewidth is a linear function of measuring frequency in a broad band measurement. We observe the nonlinear ferromagnetic resonance linewidth of Co₂MnSi thin films with respect to measuring frequency in broad band measurement. Experimental data could be well fitted with the model including two-magnon scattering with no fixed parameters. The fitting results show that two-magnon scattering results in the nonlinear linewidth behavior, and the Gilbert damping factor is much smaller than reported ones, indicating that our Co₂MnSi films are more suitable for the applications of spin transfer torque.