Study of Some Ce Intermetallics by Core Level Photoemission

Ce intermetallics CeAlNi, CeAlCu and CeNi2Si2 have been studied by core-level photoemission spectroscopy to investigate their electronic structure. The Ce 3d xps data clearly indicate that the final state is a quantum mechanical admixture of 4f0, 4f1 and 4f2 configurations in these systems with an increasing 4f0 contribution as Cu is replaced by Ni. The two Ni-based systems are found to be mixed-valence systems with n(f) < 1 while the ground state of the Cu-containing system appears to retain a purely trivalent character with n(f) congruent-to 1. These results are in agreement with our earlier reported x-ray absorption and resonant photoemission data. The present study highlights the fact that the replacing of Ni by Cu seems to be propitious for driving the Ce from an intermediate-valence (IV) to a non-IV ground state. The results of Ce 3d and Ce 4d xps are discussed.