The study on ferromagnetic resonance linewidth for NM/80NiFe/NM (NM = Cu, Ta, Pd and Pt) films

The out-of-plane angular dependence of ferromagnetic resonance (FMR) was me asured for NM/80NiFe(Py)/NM (NM = Cu, Ta, Pd and Pt) films with various Py, Cu and Ta thicknesses fabricated by magnetron sputtering. The out-of-plane angular dependences of FMR resonance field and linewidth were analyzed usi ng Landau-Lifshitz-Gilbert equation taking account of broadening of linewid th due to magnetic inhomogeneities in a film. Magnetic inhomogeneities were assumed to be the fluctuation of magnitude and direction of the effective demagnetization held which contains both demagnetization and perpendicular anisotropy field for a film. The calculations of the angular variations of linewidth agreed with the experimental ones quantitatively. The fluctuation s of magnitude and direction of the effective demagnetization field, which are represented as Delta (4 pi M-eff.) and Delta theta (H), respectively, i ncreased with decreasing Py thickness for all NM/Py/NM films, Delta theta ( H) increased as the thicknesses of the buffer layers increased for Cu/Py(40 Angstrom)/Cu films and was almost constant with increasing buffer layer th ickness for Ta/Py(40 Angstrom)/Ta films. Only in the case of NM = Pd and Pt films, the Gilbert damping parameter, which is the speed of decay of magne tization precession, was enhanced significantly as compared with that for t he bulk sample and was dependent on Py thickness.