ELECTRON-SPECTROSCOPY STUDIES ON AMORPHOUS GDFE AND GDCO ALLOYS

In situ XPS photoelectron studies on amorphous thermally evaporated GdFe and GdCo films have been made under UHV conditions. The results were used to test the conventional concept of charge transfer, which had been applied to the materials under discussion. The XPS binding energies were found to be identical in the pure elements and the alloys, suggesting that the core levels in a-GdFe and a-GdCo are not very sensitive to a change in the chemical environment. Thus, it was concluded that the transfer of charge from Gd to the transition metal d bands, if existing at all, must be smaller than one electron per Gd atom. The preferential oxidation of Gd in GdFe and GdCo films was found to be characteristically reflected in the low-energy transitions of the Auger spectra, which hence were used to distinguish between the clean and the oxidized state of Gd. The influence of oxidation from the Gd 4d and 4f levels was characterized in some separate experiments on pure Gd.