Surface response of exchange- and dipolar-coupled ferromagnets: Application to light scattering from magnetic surfaces

Abstract

We present the theory of the surface response of a semi-infinite ferromagnet in the presence of both exchange and dipolar coupling, within a continuum theory. The results are applied to a detailed study of the spectral density of surface spin fluctuations. From this we analyze the influence of exchange coupling and surface spin pinning on the frequency, linewidth, and line shape of the Damon-Eshbach surface spin wave, for a number of propagation angles, and for wavelengths sufficiently short that the exchange contribution to the energy of the wave is comparable to the Zeeman and dipolar energies. We also develop the theory of Brillouin scattering from spin waves near magnetic surfaces, and calculate the spectum of scattered light for experimentally interesting geometries, with recent light scattering studies of ferromagnetic surfaces in mind.