Ferromagnetic resonance and damping in granular Co–Cr films with perpendicular anisotropy

The 17.3 GHz ferromagnetic resonance field (HFMR) and linewidth (ΔH) have been measured as a function of the angle (θH) between the external magnetic field and film normal for a 16 nm thick Co–Cr granular film with uniaxial perpendicular anisotropy. The HFMR(θH) response is significantly different from the uniform rotation prediction. The ΔH(θH) dependence shows major deviations from the Gilbert phenomenological damping model. Both dependences can be modeled simultaneously through a combination of two-magnon scattering processes, inhomogeneity line broadening, and an intrinsic damping from magnon-electron scattering processes, with a Gilbert damping α-value of 0.004.