Effect of alloying on the electronic structure in CeNiSn

The electronic structure of CeNi_1-x{Cu}ₓ$Sn system and ${Ce}0.9Zr0.1NiSn is studied by photoemission spectroscopy. CeNiSn is a rare example of a valence-fluctuating Ce compound with a small gap at the Fermi energy. The gap is strongly suppressed by substituting either Cu for Ni or Zr for Ce. The XPS valence-band spectra are compared with ab initio band structure calculations, using the linearized muffin-tin orbital method. For CeNiSn a small indirect energy gap and a very low density of states at the Fermi level is found. The substitution of Ni by Cu leads to a higher density of states at Fermi energy, whereas for the substitution of Ce by even 10% Zr, the changes of the density of states at εF are clearly visible. A strong hybridization of the f orbitals with a conduction band is characteristic for all of the investigated compounds. We report the Ce 3d XPS spectra of CeNi_1-x{Cu}ₓ$Sn and ${Ce}0.9Zr0.1NiSn. Applying the Gunnarsson-Sch\"onhammer model the coupling energy {Δ} between the f levels and the conduction states is about 115 meV. The number of 4f electrons nf is 0.95 for CeNiSn. With increasing Cu concentration, nf is close to 1. The magnetic susceptibility of CeNi_1-x{Cu}ₓ$Sn and ${Ce}0.9Zr0.1NiSn is measured in magnetic fields from 50 Oe up to 5 T. {} 1996 The American Physical Society.