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 M-5,M-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 2.20 mu(B) (corresponding to similar 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 similar to 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 N-5,N-4 and the M-5 edges, showing that the Ce 4f states are composed of the features predicted by the single-impurity Anderson model, i.e., a broad 4f(0) peak centered at 1.9 eV and two 4f(1) 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.