In this paper, we present a resonant photoemission study of the cerium 4$f$ spectral function in Ce/Fe(100) interfaces. By covering cerium ultrathin films with lanthanum, we completely suppress the surface contribution of the spectra. Then we show that the cerium atoms at the interface are in an intermediate valent state, whereas the $f^1$ configuration is stabilized in the top layer. This method allows us to obtain the genuine 4$f$ spectral function of the interface, and could be extended to a study of Ce-based compounds.

• Received 23 July 1997

DOI:https://doi.org/10.1103/PhysRevB.56.12054