Effect of alloying on the electronic structure in CeNiSn

The electronic structure of ${\mathrm{CeNi}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Cu}}_{\mathit{x}}$Sn system and ${\mathrm{Ce}}_{0.9}$ ${\mathrm{Zr}}_{0.1}$NiSn 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 ${\mathrm{\epsilon }}_{\mathit{F}}$ 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 ${\mathrm{CeNi}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Cu}}_{\mathit{x}}$Sn and ${\mathrm{Ce}}_{0.9}$ ${\mathrm{Zr}}_{0.1}$NiSn. Applying the Gunnarsson-Schönhammer model the coupling energy Δ between the f levels and the conduction states is about 115 meV. The number of 4f electrons ${\mathit{n}}_{\mathit{f}}$ is 0.95 for CeNiSn. With increasing Cu concentration, ${\mathit{n}}_{\mathit{f}}$ is close to 1. The magnetic susceptibility of ${\mathrm{CeNi}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Cu}}_{\mathit{x}}$Sn and ${\mathrm{Ce}}_{0.9}$ ${\mathrm{Zr}}_{0.1}$NiSn is measured in magnetic fields from 50 Oe up to 5 T. © 1996 The American Physical Society.