Stabilization of Kondo semiconductor state by Sb doping of CeNi1-delta Sn1+delta and the general criterion of its appearance

Abstract

Semimetallic off-stoichiometric CeNi1¡±Sn1+±¡xSbx system with ± ¼ 0:06 is shown to transform into a Kondo semiconductor upon the substitution of few percent of Sb for Sn. The full-gap formation is associated with f-electron localization induced by the combined effect of the collective Kondo-singlet formation and the atomic disorder. Namely, the extra valence electrons introduced with the Sb doping (one per Sb atom) contribute additionally to the formation of the collective Kondo spin-singlet state at low temperatures, as seen by a substantial reduction of the magnetic susceptibility. The precise general definition of the Kondo semiconductor is provided and the difference with either the simple band or the Mott{Hubbard insulators is stressed.