Determination of the surface and bulk 4f spectral functions in Ce-Ir compounds

The surface electronic structure of two Ce-Ir compounds, CeIr5 and Ce7Ir3, is investigated by means of valence band resonant photoemission at the Ce 3d-4f and Ce 4d-4f thresholds, By taking advantage of the different surface sensitivity at the two thresholds, the 4f spectral weight has been decomposed into a surface and a bulk component, For both compounds, an increased localization of the 4f orbitals in the surface layers is observed, accompanied by a decreased hybridization with the valence band states. From the comparison between the two compounds, the different distribution of the 4f spectral weight between the 4f(0) and 4f(1) final states is interpreted by means of the difference in stoichiometry and crystal structure, which results in a different degree of f-d hybridization. A surface core level shift in the 4f(0) final state is moreover observed for Ce7Ir3.