Mixed Valence of Ce and Its Consequences on the Magnetic State of Ce9Ru4Ga5: Electronic Structure Studies

We report on X-ray photoelectron spectroscopy (XPS) and ab initio electronic structure investigations of a novel intermetallic material Ce9Ru4Ga5. The compound crystallizes with a tetragonal unit cell (space group I4mm) that contains three inequivalent Ce atoms sites. The Ce 3d core level XPS spectra indicated an intermediate valence (IV) of selected Ce ions, in line with the previously reported thermodynamic and spectroscopic data. The ab initio calculations revealed that Ce1 ions located at 2a Wyckoff positions possess stable trivalent configuration, whereas Ce2 ions that occupy 8d site are intermediate valent. Moreover, for Ce3 ions, located at different 8d position, a fractional valence was found. The results are discussed in terms of on-site and intersite hybridization effects