Light scattering from spin wave excitations in a Co/CoPt exchange spring

We have developed a theory of Brillouin light scattering (BLS) from spin wave excitations in non-collinear magnetisation structures. We compare the results of calculated spectra for scattering from the spiral state found in exchange-coupled hard/soft CoPt/Co bilayers during reversal with experimental data. Both the Stokes/anti-Stokes peak intensity ratio is described, as well as the asymmetry in peak frequency between the Stokes and anti-Stokes spectra. It is shown that the frequency asymmetry arises naturally in the presence of a spin spiral structure.