Non-Fermi-liquid behavior and spin fluctuations in doped UAl2

Using the canonical spin-fluctuation system UAl2 as a starting point, via negative chemical pressure (doping with Y) we have expanded dU-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 γ (≡C/TlimT→0), and spin-fluctuation temperature, behave monotonically. For U1-xYxAl2, 0.30≤x≤0.70, spin-glass behavior is found with Tf≅;5.1±0.5 K. This spin-glass behavior weakens (Tf sinks, smaller magnetic signature, no specific-heat anomaly) for x≥0.75 while, at the same time, the spin-fluctuation T3lnT term also gradually disappears from the specific heat. For x≥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 1997 The American Physical Society