BRILLOUIN LIGHT-SCATTERING INTENSITIES FOR A THIN-FILM EXCHANGE-COUPLED TO A BULK MAGNETIC SUBSTRATE

Brillouin light scattering intensities vs. frequency shift have been c alculated for a complex structure consisting of a bulk magnetic substr ate, a nonmagnetic spacer layer, a thin magnetic film a few monolayers thick, and a thin nonmagnetic overlayer. The calculations have been c arried out for the back-scattering configuration with an applied magne tic field in the plane of the specimen using a modification of the for malism described by Camley and Mills. The thin film magnetization has been assumed to be coupled to the bulk surface magnetization by an exc hange energy of the form E-x = - J(1) cos theta + J(1) cos(2) theta er g/cm(2), where theta is the angle between the directions of the thin f ilm magnetization and the bulk surface magnetization. The theory gives a good account of the field-dependent frequency shifts measured using Fe(001) whisker/Cr(001)/Fe(001)/Au(001) structures. Such experiments can be used to obtain values for the coupling parameters, J(1) and J(2 ), without having to use micromagnetic calculations to interpret the a pplied field dependence of the thin film and bulk magnetization orient ations. The theory can also be used to obtain the total coupling stren gth, J(EX) = J(1) - 2J(2), even when this coupling strength is positiv e, corresponding to ferromagnetic coupling, provided that J(EX) is not too strong(similar to 1 erg/cm(2) or less for the whisker/Fe system).