Brillouin light scattering cross section in Fe(110)/Cu(111)/Fe(110) asymmetric bilayers

A detailed study of the Brillouin scattering cross section from spin waves has been carried out for Fe~110!/Cu~111!/Fe~110!/Si~111! heterostructures, with thickness of the two Fe layers of 20 Å and 60 Å, and interlayer Cu thickness variable in the range 0-33 Å. We found that for thicknesses of the Cu spacer larger than 6 Å, the Brillouin spectrum consists of the acoustical and optical spin wave modes, whose frequency separation depends on the Cu layer thickness. A good agreement between the calculated and the measured cross sections has been obtained. An explanation of the Stokes/ anti-Stokes asymmetry of the acoustical mode is given in terms of interference effects between the contributions due to the two dynamic magnetization components.