Stokes—anti-Stokes asymmetry in Brillouin scattering from magnons in thin ferromagnetic films

Abstract

A large asymmetry is found in the intensity between Stokes peaks and the equivalent anti-Stokes peaks in scattering from magnons in very thin ferromagnetic films. It is shown that this asymmetry is due to the contribution of the off-diagonal spin-spin correlation function $〈S_x{S}_y〉$ to the light scattering intensity. This contribution is only seen when the wave vector of the light in the ferromagnet is complex, the case for absorptive materials. The asymmetry is studied both theoretically and experimentally, and good agreement is found.