Field-induced quantum criticality in CeCu6-xAux

The heavy-fermion system CeCu6-xAux is an archetype for pressure-induced quantum criticality at the onset of antiferromagnetic order. Up to now, investigations focused mainly on the behavior close to the critical concentration xc∼0.1. The antiferromagnetic order of samples with higher Au content can, however, be also suppressed by magnetic fields. We studied the field-induced quantum critical behavior of samples with Au contents x=0.3, 0.5 and 1.0 in fields applied along the magnetic easy axis by using thermal expansion and magnetostriction measurements. Due to their high sensitivities these measurements are especially suited to expose deviations from Fermi-liquid behavior. The measurements have been performed for temperatures ranging between 20 mK and 10 K, and in magnetic fields up to 14 T. With increasing Au content and critical field Bc they show strongly varying critical behavior. We discuss our results taking into account the field-dependent Zeeman splitting of the CEF ground-state doublet, which manifests itself as a Schottky-like anomaly at low temperatures and fields larger than Bc.