G. Chełkowska

The mixed-valence state of Ce in the hexagonal CeNi4B compound

Measurements of the magnetic susceptibility χ, x-ray photoemission spectra (XPS), electrical resistivity ρ and electronic structure calculations for CeNi4B are reported. In the paramagnetic region, CeNi4B follows the Curie–Weiss law with µeff = 0.52µB/fu and θ = −10.7 K. The effective magnetic moment is lower than the free Ce3+-ion value. The Ce(3d) XPS spectra have confirmed the mixed-valence state of Ce ions in CeNi4B. The f occupancy, nf, and the coupling Δ between the f level and the conduction states were derived to be about 0.83 and 85 meV, respectively. Both susceptibility data and XPS spectra show that Ce ions in CeNi4B are in the intermediate-valence state. At low temperatures (below 12 K), the magnetic contribution to the electrical resistivity reveals a logarithmic slope characteristic of Kondo-like systems.

XPS studies of the hybridization effects in RNi4B (R=Ce, Pr, Nd) compounds

Abstract We report new results on X-ray photoemission spectroscopy (XPS) studies of CeNi 4 B. For comparison the PrNi 4 B and NdNi 4 B intermetallic compounds are investigated. Core-levels and valence bands were investigated. The valence band spectra of RNi 4 B are established mainly by R(4 f ) and Ni(3 d ) states. The XPS spectra of the 3 d 5/2 and 3 d 3/2 states reveal additional satellites, which, basing on the Gunnarsson–Schonhammer model, enable the estimation of the coupling between the f -orbitals and the conduction states, Δ ≈85xa0meV, 63xa0meV and 23xa0meV for CeNi 4 B, PrNi 4 B and NdNi 4 B, respectively. The value of the 3 d spin–orbit splitting E LS for R=Ce, Pr and Nd is equal to 18.4, 20.8 and 22.8xa0eV, respectively.