Ferromagnetic resonance linewidth and two-magnon scattering in Fe1-xGdx thin films

Magnetization dynamics of Fe1-xGdx thin films (0 ≤ x ≤ 22%) has been investigated by ferromagnetic resonance (FMR). Out-of-plane magnetic field orientation dependence of resonance field and linewidth has been measured. Resonance field and FMR linewidth have been fitted by the free energy of our system and Landau-Lifshitz-Gilbert (LLG) equation. It is found that FMR linewidth contains huge extrinsic components including two-magnon scattering contribution and inhomogeneous broadening for FeGd alloy thin films. In addition, the intrinsic linewidth and real damping constants have been obtained by extracting the extrinsic linewidth. The damping constant enhanced from 0.011 to 0.038 as Gd dopants increase from 0 to 22% which originates from the enhancement of L-S coupling in FeGd thin films. Besides, gyromagnetic ratio, Landé factor g and magnetic anisotropy of our films have also been determined.