  Soft x-ray fluorescence spectroscopy has been employed to obtain information
about the Si-derived valence band states of Fe/Si multilayers. The valence band
spectra are quite different for films with and without antiferromagnetic
interlayer exchange coupling, demonstrating that these multilayers have
different silicide phases in their spacer layers. Comparison with previously
published fluorescence data on bulk iron silicides shows that the Fe
concentration in the silicide spacer layers is substantial. Near-edge x-ray
absorption data on antiferromagnetically coupled multilayers in combination
with the fluorescence data demonstrate unambiguously that the silicide spacer
layer in these films is metallic. These results on the electronic structure of
buried layers in a multilayer film exemplify the wide range of experiments made
possible by new high-brightness synchrotron sources.
