Muon-spin-relaxation studies on the heavy-fermion system with non-Fermi-liquid behaviorCeCu5.9Au0.1

Positive muon-spin-relaxation (μSR) measurements have been carried out down to 20 mK on a single crystal of the heavy-fermion system ${\mathrm{CeCu}}_{5.9}$ ${\mathrm{Au}}_{0.1}$, which exhibits non-Fermi-liquid behavior. Whereas preliminary μSR studies on the isostructural compound ${\mathrm{CeCu}}_5$Au confirms the previously reported development of an incommensurate antiferromagnetic state for this Au concentration, the zero-field data on ${\mathrm{CeCu}}_{5.9}$ ${\mathrm{Au}}_{0.1}$ show no sign of magnetic ordering down to the lowest temperature investigated, setting an upper limit of 0.003${\mathrm{\mu }}_{\mathit{B}}$ for a hypothetical static Ce moment. This observation by a microscopic technique supports the assertion that non-Fermi-liquid behavior is observed in Kondo lattices when magnetic order is homogeneously suppressed to zero temperature, i.e., at a quantum phase transition between magnetic and nonmagnetic ground states.