Electronic structure of CeCo1−xFexGe3 studied by X-ray photoelectron spectroscopy and first-principles calculations

Abstract

A transformation between the magnetically ordered CeCoGe3 and heavy fermion CeFeGe3 is isostructural but not isoelectronic, therefore the characterization of the electronic structure of the CeCo1−xFexGe3 series is of special importance. We report both the experimental investigation by the X-ray photoelectron spectroscopy (XPS) measurements and the first-principles calculations within the full-potential local-orbital (FPLO) scheme based on the density functional theory. Experimentally, we investigate mainly the valence band and the Ce 3d spectra, both giving the possibility to conclude about the level of the f states localization. Computationally, we investigate the most characteristic CeCoGe3, CeCo0.5Fe0.5Ge3, and CeFeGe3 compositions. Based on the electronic band structure results we calculate the X-ray photoelectron spectra of the valence band. We consider the effects of the spin-orbit coupling and intra-atomic Hubbard U repulsion. Furthermore, we discuss the charge distribution and occupation of valence-band orbitals. The experimentally observed evolution of the 3d band with the Fe concentration is related to the decrease of the number of electrons and reduction of the 3d photoionization cross-sections. Calculations indicate that charge is transferred mainly from the Ce to Ge sites and the bondings are formed mainly by the Ce 5d, Fe/Co 3d, and Ge 4p and Ge 4s orbitals.