Evolution from first-order valence transition to heavy-fermion behavior in YbIn1-xAgxCu4.

Abstract

${\mathrm{YbInCu}}_{4}$ undergoes a first-order isostructural valence transition near 40 K, whereas ${\mathrm{YbAgCu}}_{4}$ is a moderately heavy (\ensuremath{\gamma}=250 mJ/mol ${\mathrm{K}}^{2}$) mixed-valence compound. We have succeeded in growing single crystals of these compounds, as well as many intermediate alloys, using flux-growth techniques. The evolution from ${\mathrm{YbInCu}}_{4}$ to ${\mathrm{YbAgCu}}_{4}$ has been characterized using electrical resistivity, magnetic susceptibility, and x-ray powder diffraction. The data are interpreted in terms of the evolution of the single-impurity Kondo temperature as a function of Ag concentration. \textcopyright{} 1996 The American Physical Society.