NON-FERMI-LIQUID BEHAVIOR IN MAGNETIC D-ELECTRON AND F-ELECTRON SYSTEMS

A growing number of metals have been found to show systematic deviatio ns from the predictions of Landau Fermi-liquid theory. The most straig htforward examples are magnetic metals in which the Curie (T-C) or Nee l (T-N) temperature has been suppressed to 0 K by the application of h ydrostatic pressure. Such systems are discussed here within a spin flu ctuation framework which provides quantitatively accurate descriptions of the d-electron systems MnSi and ZrZn2 near their 'quantum critical points', but which appears to be less successful (in its simplest for m) in antiferromagnetic f-electron systems, particularly CePd2Si2, whi ch at its critical pressure has a resistivity of the form Delta rho pr oportional to T1.2+/-0.1 over a temperature range extending from aroun d 40 K to below 1 K. CeNi2Ge2, which is believed to be close to a quan tum critical point at ambient pressure, shows similar behaviour. CeIn3 , CePd2Si2 and CeNi2Ge2 exhibit superconductivity, in the first two ca ses limited to a narrow region near the critical pressure, making thes e the first unambiguous examples of magnetically mediated superconduct ivity. (C) 1998 Elsevier Science B.V. All rights reserved.