Magnetic and transport properties of cubic AuBe5-type YbCu5-xGax system

YbCu5-xGax (0 less than or equal to x less than or equal to 0.7) system wit h cubic AuBe5-type structure has been prepared for the first time by means of high-pressure technique, in addition to previously reported cubic YbCu5 and YbCu5-xAlx. The maximum (T-max similar to 10 K) in susceptibility-tempe rature curve of cubic YbCu5, which is due to Kondo lattice formation, disap pears thoroughly even upon slight Cu/Ga substitution. For samples with x gr eater than or equal to 0.1, Curie-Weiss behavior was observed over the whol e measured temperature range with the effective magnetic moment estimated t o be very close to 4.54 mu (B) of a free Yb3+ ion. Unlike similar Curie-Wei ss behavior, their electrical resistivity-temperature curves suggest a syst ematic evolution from a temperature square power p similar to T-2 dependenc e for x = 0.0 to a negative logarithmic temperature rho similar to -log T d ependence for x = 0.7. The Cu/Ga substitution therefore drives the system t o experience a crossover from a typical Kondo lattice behavior to a single- impurity Kondo behavior, meanwhile the characteristic Kondo temperature T-K is lowered greatly. The electronic effect rather than the lattice volume e ffect is likely responsible for such a crossover caused by Cu/Ga substituti on. (C) 2001 Elsevier Science B.V. All rights reserved.