Electronic structure studies of CeRhSb with Rh substituted by Pd and Ni

Abstract

We have investigated the influence of the valence of Ce ions on the gap formation in CeRhSb-type Kondo insulators. We present the $3d$ x-ray photoemission spectroscopy (XPS) spectra for CeRhSb, ${\mathrm{CeRh}}_{1\ensuremath{-}x}{\mathrm{Pd}}_{x}\mathrm{Sb},$ and ${\mathrm{CeRh}}_{1\ensuremath{-}x}{\mathrm{Ni}}_{x}\mathrm{Sb}$ compounds. From the experimental Ce $3d$ XPS spectra we extracted the spectral weight of the different ${3d}^{9}{f}^{0},$ ${3d}^{9}{f}^{1},$ and ${3d}^{9}{f}^{2}$ final states. We used the Doniach-\ifmmode \check{S}\else \v{S}\fi{}unji\ifmmode \acute{c}\else \'{c}\fi{} method to separate the overlapping peaks in the $3d$ XPS spectra. Analysis of the ${3d}^{9}{f}^{2}$ weight using Gunnarsson-Sch\"onhammer theory suggests a hybridization interaction $\ensuremath{\Delta}$ of about 150 meV for CeRhSb. The hybridization energy $\ensuremath{\Delta}$ obtained for CeNiSb and CePdSb is $\ensuremath{\sim}3$ times smaller than that of the Kondo insulating compound CeRhSb. Analysis of the ${3d}^{9}{f}^{0}$ component indicates a mixed valence of Ce in CeRhSb, and a stable configuration of Ce in the Ni or Pd alloys. The experimental results indicate the influence of atomic disorder on the magnetic behavior of CePdSb and CeNiSb.