Kondo ground states and non-Fermi-liquid behavior inCeNi1−xCoxGe2

Abstract

We report measurements of the magnetic susceptibility, specific heat, and electrical resistivity of the heavy fermion alloy series $\mathrm{Ce}{\mathrm{Ni}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}{\mathrm{Ge}}_{2}$. With increasing $x$, hybridization between the localized $4f$ and conduction band electrons is enhanced. The magnetic order observed at $x=0$ is completely suppressed at $x=0.3$ and non-Fermi-liquid behavior appears at the critical concentration, which is analyzed in terms of two-dimensional antiferromagnetic quantum fluctuations. Specific heat and magnetic susceptibility data are quantitatively explained by the Coqblin-Schrieffer model with degenerate impurity spin $j=1∕2$, $3∕2$, and $5∕2$ for Co concentration range of $x\ensuremath{\leqslant}0.6$, $0.7\ensuremath{\leqslant}x\ensuremath{\leqslant}0.8$, and $x\ensuremath{\geqslant}0.9$, respectively.