Second order magneto-optic effects in Brillouin scattering from spin waves in magnetic multilayers

The Brillouin light scattering cross section from a thick magnetic multilayer has been calculated using a theoretical model based on a macroscopic partial waves approach for the calculation of the normal modes. Special attention has been paid to analyzing the effect of inclusion of the second order magneto-optic constant in addition to the first order one ~corresponding to Voigt and Faraday effects, respectively!. This model has been exploited to analyze the experimental Brillouin spectra measured from a several nm thick Ni/Cu bilayer. Both surface and bulk standing spin waves have been experimentally detected for different incident angles and applied magnetic fields ~including field reversal!. The measured spectra can be satisfactorily reproduced by our model, allowing the determination of magnetic and magneto-optic parameters of the samples.