BRILLOUIN LIGHT-SCATTERING ON FE CR/FE THIN-FILM SANDWICHES/

Brillouin light scattering (BLS) in the backscattering configuration h as been used to study the magnetic excitations in epitaxial Fe(38 angs trom)/Cr(13 angstrom)/Fe(38 angstrom) thin-film sandwiches. Spin-wave frequency was measured versus in-plane wave vector k and static in-pla ne magnetic field H for both [100] and [110] direction fields and k pe rpendicular to H. The range of applied fields was 50-1500 Oe. The wave -number range was 0.45 X 10(5)-2.3 X 10(5) rad/cm. The BLS spectra cor relate with magnetization versus field profiles and confirm the antife rromagnetic coupling between the Fe layers. Under low-field conditions and near-antiparallel alignment of the Fe layer magnetization vectors , the spin-wave frequencies from the Stokes and anti-Stokes sides of t he BLS spectra are different. These frequencies merge at high field. T he low-field splitting feature is very sensitive to small differences in thickness for the magnetic layers and indicates a thickness differe nce of 9%. Matchups between features of the BLS data and magnetization curves were obtained for the following parameters: magnetic layer sat uration induction 4piM(s)=18.6 kG; cubic anisotropy field H(A)=550 Oe; in-plane [110] uniaxial anisotropy field H(U)=76 Oe; antiferromagneti c interlayer exchange coupling field H(J)=120 Oe. Spin-wave frequency calculations based on these parameters show quantitative agreement wit h the measurements. The quantitative fits required inclusion in the th eory of an iron layer surface anisotropy with an effective surface ani sotropy field of 2 kOe.