Influence of yttrium substitution on the magnetic and transport properties of UCu5

We have measured the resistivity, magnetoresistance, resistivity under hydrostatic pressure and the magnetization of the compound (U1-xYxCu5 for temperatures between 0.4 and 300 K, fields of up to 12 T and at pressures between 1 bar and 14 kbar. From this series of measurements we have derived compositional, H-T and p-T phase diagrams. Using thermodynamic arguments and a comparison of these phase diagrams we arrive at a nomenclature for the various phases which is consistent with that used for the parent compound UCu5. We observe that the 1-q structure observed below T2 = 1.16 K in UCu5 is stabilized with increasing yttrium. In addition the introduction of yttrium results in a rapid reduction of TN. The effects of 'chemical' pressure are found to be opposite to those observed for hydrostatic pressure, which enhances TN and reduces T2. From an analysis of the dc susceptibility we derive values for χ0 (Pauli susceptibility) which indicate a large reduction of the density of states for x>0.1 and this is consistent with the reduction 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 contribution. An analysis of the resistivity and ΘP (paramagnetic Curie-Weiss temperature) for (U0.7Y0.3)Cu5 is consistent with the onset of a Kondo process with increasing yttrium doping. (author)