Transport and magnetic properties of UCu(5-x)M(x) (M=Pd, Pt)

The substitution of transition metals for Cu in the heavy-fermion compound UCu5 leads to unusual low-temperature properties. For example, the substitution of Pd suppresses long-range magnetic order and results in non-Fermi-liquid behaviour. In this report, we compare properties and phase diagrams for UCu5-xPdx and UCu5-xPtx based upon electrical resistivity and de magnetic susceptibility measurements. In the Pt system, we find a rapid suppression of magnetic ordering similar to that seen in the Pd system. The electrical resistivity and de magnetic susceptibility of UCu5-xPtx exhibit low-temperature behaviour (T less than or equal to 10 K) for x greater than or equal to 0.75 suggestive of the non-Fermi-liquid behaviour found in UCu5-xPdx for 1 less than or equal to x less than or equal to 1.5. The electrical resistivity of UCu5-xPtx for 0.75 less than or equal to x less than or equal to 1.75 reaches a concentration-dependent minimum before increasing at lower temperatures. At higher Pt concentrations (x greater than or equal to 2), the electrical resistivity develops a broad peak at low temperatures, as in UCu5-xPdx. suggesting short-range magnetic order although irreversibility was not seen in the magnetic susceptibility. The similarities of and differences between the two systems are discussed. The possibility of non-Fermi-liquid behaviour in UCu5-xPtx is considered.