Exchange bias of NiO/NiFe: Linewidth broadening and anomalous spin-wave damping

We studied sputtered NiO(150 nm)/NiFe exchange-biased films using Network Analyzer ferromagnetic resonance spectroscopy (NA-FMR) and Brilliouin light scattering (BLS) techniques. The complex permeability spectra were obtained for NiO/NiFe films and were fitted to the Landau-Lifshitz-Gilbert equation to determine intrinsic and extrinsic contribution to Gilbert damping, in addition to other magnetic parameters. The exchange anisotropy (H-EX) was determined from the field variation data of NA-FMR resonance frequency (f(res)) and BLS mode frequency (f(m)). H-EX was observed to decreases as 1/thickness, from where we derive macroscopic interfacial exchange energy J(E)=0.021 erg/cm(2). Second, we investigated the relaxation mechanism in NiO/NiFe films from NA-FMR linewidth (Deltaf(res)) for wave vector k=0 mode and from BLS mode linewidth (Deltaf(m)) for knot equal0 modes. Interestingly, we observed Deltaf(res) to increase with increasing magnetic field but Deltaf(m) was observed to decrease with increasing magnetic field. Therefore, it is confirmed that, the relaxation rate measured by FMR and BLS techniques is different. Deltaf(res) was observed to increase with decreasing NiFe thickness and follows a t(-2) fit function, from which we determine the local interfacial exchange energy J(1)=3.3 erg/cm(2). (C) 2003 American Institute of Physics.