Intermediate valence in the filled skutterudite compoundYbFe4Sb12

Abstract

We have synthesized and characterized ${\mathrm{YbFe}}_4{\mathrm{Sb}}_{12},$ a member of the class of filled skutterudite (${\mathrm{LaFe}}_4{\mathrm{P}}_{12}$-type) compounds. Measurements of the lattice parameter, magnetization, electrical resistivity, and specific heat suggest that the Yb ions have an intermediate valence and that the effective mass of the conduction electrons is moderately enhanced at low temperatures. The coefficient of the electronic specific heat is estimated to be $\gamma \mathrm{}\left(0\right)=140\mathrm{}{\mathrm{mJ}\mathrm{}\mathrm{mol}}^{\mathrm{-}1}{\mathrm{}\mathrm{K}}^{\mathrm{-}2},$ and we observe a characteristic temperature for the Yb ion valence fluctuations of $T^{*}\sim 50\mathrm{K}.$ No superconductivity was detected down to $T=0.40\mathrm{}\mathrm{K}.$