Nuclear magnetic resonance and pressure effects in UNi5-5xCu5x

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Abstract
An investigation is reported in which various polycrystalline compounds in the series UNi5-5xCu5x (cubic AuBe5 structure) were studied by means of Cu NMR. The Cu resonance of atoms residing at the site of trigonal point symmetry was observed only in UCu5, as a pure quadrupole resonance (NQR). The Cu resonance due to atoms at the site of cubic point symmetry was observed in compounds of various compositions. From the compositional variation of the linewidth of this latter resonance it was found that the Cu atoms have a strong preference to occupy the cubic site. The Knight shift in UCu5 was found to scale linearly with the susceptibility. The effect of external pressure on the room-temperature resistivity was studied in UNi2Cu3, UNiCu4, and UCu5. It is weak and negative in the first compound but strong and positive in the two latter compounds. These results indicate that the configurational crossover is already occurring at Cu concentrations <or=0.8.