Evidence for strongf−dhybridization in the intermetallic ferromagnetCePdIn2

Abstract

We have investigated the contribution of Ce $4f$ states to the electronic structure of the intermetallic ferromagnet ${\mathrm{CePdIn}}_{2}$ by means of x-ray absorption spectroscopy and resonant and nonresonant photoemission spectroscopy. The line shape of the Ce ${M}_{5,4}$ 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 $2.20{\ensuremath{\mu}}_{B}$ (corresponding to $\ensuremath{\sim}87%$ 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 $\ensuremath{\sim}180$ meV, revealing that ${\mathrm{CePdIn}}_{2}$ is a strongly hybridized system. This is consistent with the results from the analysis of the resonant valence band photoemission measurements at both the ${N}_{5,4}$ 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 $4{f}^{0}$ peak centered at 1.9 eV and two $4{f}^{1}$ 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.