Brillouin scattering of light by spin waves in thin ferromagnetic films (invited)

Abstract

The new technique of Brillouin scattering from spin waves has been applied to thin ferromagnetic films. Scattering from standing spin waves and the Damon Eshbach (DE) surface wave is observed. The interaction of both types of waves at a mode crossing in Fe films under variation of the thickness d is investigated. The results suggest the absence of surface anisotropy and pinning. For d≲20 nm scattering from standing modes becomes too weak to be observed. In contrast to this, for the DE mode there is a strong increase in the scattering intensity when the films have been evaporated onto the proper substrates. It is shown that this is due to both an increase in the thermal DE mode amplitudes and multiple interference effects in the lightscattering process. Very strong scattering is obtained from films with d≊5 nm. There is also a remarkable Stokes-Antistokes asymmetry, which persists down to d≲3 nm. It comes from the elliptical spin-precession characteristic for such small values of d and the strong metallic attenuation of the light. The technique has also been applied to an investigation of the coupling of DE modes in double layer systems.