HEAVY-FERMION SYSTEMS AT THE MAGNETIC-NONMAGNETIC QUANTUM PHASE-TRANSITION

Heavy-fermion systems are characterized by their proximity to magnetic order which can often be induced or suppressed by changing a paramete r such as concentration or pressure. Hence, these systems provide idea l testing grounds for a magnetic phase transition occurring at T = 0 a s a function of these parameters. We will review the salient features of the exemplary system CeCu6-xAux where antiferromagnetism can be ind uced by alloying with Au above a critical concentration x(c) = 0.1. At the quantum-critical point x = x(c), unusual features are observed, e .g, a specific-heat coefficient gamma = ln(T/T-0) that diverges logari thmically for T --> 0, and a resistivity Delta rho varying linearly wi th T, in marked contrast to the canonical Fermi-liquid behaviour. (C) 1998 Elsevier Science B.V. All rights reserved.