Influence of yttrium substitution on the magnetic and transport propertiesof UCu5

We have measured the resistivity, magnetoresistance, resistivity under hydr ostatic pressure and the magnetization of the compound (U1-xYx)Cu-5 for tem peratures between 0.4 and 300 K, fields of up to 12 T and at pressures betw een 1 bar and 14 kbar. From this series of measurements we have derived com positional, H-T and p-T phase diagrams. Using thermodynamic arguments and a comparison of these phase diagrams we arrive at a nomenclature for the var ious phases which is consistent with that used for the parent compound UCu5 . We observe that the 1-g structure observed below T-2 = 1.16 K in UCu5 is stabilized with increasing yttrium. In addition the introduction of yttrium results in a rapid reduction of T-N The effects of 'chemical' pressure are found to be opposite to those observed for hydrostatic pressure, which enh ances T-N and reduces T-2. From an analysis of the de susceptibility we der ive values for Xo (Pauli susceptibility) which indicate a large reduction o f the density of states for x > 0.1 and this is consistent with the reducti on of the resistivity observed at room temperature. However, this analysis could not rule out the possibility of a change in the source of the Kondo c ontribution. An analysis of the resistivity and Thetap (paramagnetic Curie- Weiss temperature) for (U0.7Y0.3)Cu-5 is consistent with the onset of a Kon do process with increasing yttrium doping.