Non-Fermi-liquid behaviour at the pressure-induced antiferromagnetic to nonmagnetic transition in a heavy-fermion compound,

Abstract

High-pressure studies of transport, magnetic and thermal properties of a heavy-fermion antiferromagnet, , are reviewed. At ambient pressure, the Ce ions in the three nonequivalent sites in this compound are found to be very close to trivalent from -XANES (x-ray absorption near-edge structure) spectra and magnetic susceptibility measurements. With increasing pressure, (1.8 K at P = 0) of is suppressed and vanishes near . Non-Fermi-liquid (NFL) behaviour appears around 0.4 GPa in both the specific heat and AC magnetic susceptibility: and ). Above 0.62 GPa, the normal Fermi liquid state recovers as indicated by the T independence of and the dependence of magnetic resistivity. The variation of with pressure is analysed in terms of two models: the impurity Kondo model with three Kondo temperatures and the self-consistent renormalization (SCR) theory of spin fluctuations (SFs). We find that the crossover in is better described by the SCR theory. The characteristic SF temperature increases by a factor of 20 for 0.33 GPa , yielding a large Grüneisen parameter around 0.4 GPa.