Determination of the magnetic parameters of thin Ni films by Brillouin light scattering

The Brillouin light scattering technique has been exploited in order to investigate the magnetic properties of Ni films about 20 nm thick, deposited by thermal evaporation onto sapphire, silicon and gallium arsenide substrates. Experiments were performed in the backscattering interaction geometry, using a Sandercock type, 3+3 pass tandem Fabry-Perot interferometer. Measurement of the frequency shift of the Damon-Eshbach (DE) surface spin wave versus the applied magnetic field H-o enabled us to determine the values of characteristic magnetic parameters of the Ni films, such as the spectroscopic separation factor and the surface saturation magnetization. The former parameter is in fairly good agreement with the literature value, while the latter shows to be lower than in bulk Ni and to depend appreciably on the substrate material. In addition, the exchange stiffness constant has been evaluated by studying the dependence of the DE wave on the angle of incidence of light. This proves that a systematic study of the DE wave can provide the amount of information necessary for a complete magnetic characterization of magnetic films, even in the case of thicknesses below 30 nm, where bulk standing spin waves are not experimentally accessible.