Non-Fermi-liquid behavior and spin fluctuations in dopedUAl2

Abstract

Using the canonical spin-fluctuation system UAl{sub 2} as a starting point, via negative chemical pressure (doping with Y) we have expanded d{sub U-U} in a system known to be near the Hill limit of f-electron localization, and characterized the samples via resistivity, magnetic susceptibility, and specific-heat measurements. All system parameters, including magnetic susceptibility, specific heat {gamma} ({equivalent_to}C/Tlim{sub T{r_arrow}0}), and spin-fluctuation temperature, behave monotonically. For U{sub 1{minus}x}Y{sub x}Al{sub 2}, 0.30{le}x{le}0.70, spin-glass behavior is found with T{sub f}{approx_equal};5.1{plus_minus}0.5 K. This spin-glass behavior weakens (T{sub f} sinks, smaller magnetic signature, no specific-heat anomaly) for x{ge}0.75 while, at the same time, the spin-fluctuation T{sup 3}lnT term also gradually disappears from the specific heat. For x{ge}0.875, a non-Fermi-liquid (nFl) lnT term is found in the low temperature C/T. This new, perhaps equilibrium, ground state persists upon further dilution of the U ions with Y. Thus, we report on the evolution of nFl behavior in the neighborhood of a spin-glass ground state but, indeed, directly out of a yet weaker form of magnetism than heretofore reported, that of spin fluctuations. {copyright} {ital 1997} {ital The American Physical Society}