Non-Fermi-liquid behavior in a heavy-fermion alloy at a magnetic instability

Abstract

The specific heat C and electrical resistivity \ensuremath{\rho} of the heavy-fermion alloy ${\mathrm{CeCu}}_{5.9}$${\mathrm{Au}}_{0.1}$ exhibit non-Fermi-liquid behavior well below 1 K, i.e., C/T\ensuremath{\propto}-ln(T/${\mathit{T}}_{0}$) and \ensuremath{\rho}=${\mathrm{\ensuremath{\rho}}}_{0}$+A'T, over more than a decade in temperature T. The magnetic susceptibility \ensuremath{\chi} measured in 0.1 T shows a cusp for T\ensuremath{\rightarrow}0. This behavior is attributed to the proximity to magnetic order: In contrast to ${\mathrm{CeCu}}_{6}$, ${\mathrm{CeCu}}_{6\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Au}}_{\mathit{x}}$ alloys show long-range antiferromagnetic order, with ${\mathit{T}}_{\mathit{N}}$\ensuremath{\rightarrow}0 for ${\mathit{x}}_{\mathit{c}}$=0.1. Hence ${\mathrm{CeCu}}_{5.9}$${\mathrm{Au}}_{0.1}$ is at the edge of a zero-temperature quantum phase transition. In a large magnetic field (B\ensuremath{\ge}3 T) Fermi-liquid behavior is recovered.