Evidence for strong f-d hybridization in the intermetallic ferromagnet CePdIn2

We have investigated the contribution of Ce 4f states to the electronic structure of the intermetallic ferromagnet CePdIn2 by means of x-ray absorption spectroscopy and resonant and nonresonant photoemission spectroscopy. The line shape of the Ce M5,4 absorption edge reveals the localized nature of the 4f states, and is consistent with a predominantly 3+ ionic state for Ce ions. Fitting of the Ce 3d core level gives a Ce 4f occupation number at room temperature of 0.92, which is in good agreement with the Ce effective magnetic moment of 2.20μB (corresponding to ∼87% of the free-electron moment) as calculated from the inverse magnetic susceptibility. Moreover, the hybridization strength between 4f and conduction electrons is found to be ∼180 meV, revealing that CePdIn2 is a strongly hybridized system. This is consistent with the results from the analysis of the resonant valence band photoemission measurements at both the N5,4 and the M5 edges, showing that the Ce 4f states are composed of the features predicted by the single-impurity Anderson model, i.e., a broad 4f0 peak centered at 1.9 eV and two 4f1 spin-orbit states much closer to the Fermi level. The same spectra also show that the Ce 4f resonant spectral weight extends over a wide binding energy range, overlapping with that presumably occupied by the Pd 4d ligand states. This energy overlap is interpreted as a signature of the strong hybridization governing the system, which could possibly favor the emergence of long-range ferromagnetism through the indirect exchange between localized 4f states mediated by highly dispersive d electrons.