Ferromagnetic resonance linewidth in exchange-biased ferromagnet/antiferromagnet bilayers with ac field-cooling procedure

Out-of-plane ferromagnetic resonance spectra of Co20Ni80/FeMn bilayers with a ground state consisting of stripe ferromagnetic domains as accommodated by ac field-cooling process were measured and analyzed by the Landau–Lifshitz–Gilbert equation. One weak resonance peak that might be the surface spin-wave was observed beside the main resonance peak when the applied field was perpendicular to the film plane. In order to explain the linewidth, the extrinsic magnetic relaxation must be considered, in addition to the intrinsic Gilbert damping effect and the broadening induced by magnetic inhomogeneity. The characteristic of the extrinsic magnetic relaxation is consistent with the two-magnon scattering model.