Non-Fermi-liquid behavior and spin fluctuations in dopedUAl2

Using the canonical spin-fluctuation system ${\mathrm{UAl}}_2$ as a starting point, via negative chemical pressure (doping with Y) we have expanded ${\mathrm{d}}_{\mathrm{U}\mathrm{-}\mathrm{U}}$ 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/Ttlim ${}_{\mathrm{T}\to 0}{}^{}{}_{}{}^{}$), and spin-fluctuation temperature, behave monotonically. For ${\mathrm{U}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Y}}_{\mathrm{x}}$ ${\mathrm{Al}}_2$, 0.30⩽x⩽0.70, spin-glass behavior is found with ${\mathrm{T}}_{\mathrm{f}}$≃5.1±0.5 K. This spin-glass behavior weakens (${\mathrm{T}}_{\mathrm{f}}$ sinks, smaller magnetic signature, no specific-heat anomaly) for x⩾0.75 while, at the same time, the spin-fluctuation ${\mathrm{T}}^3$ln T term also gradually disappears from the specific heat. For x⩾0.875, a non-Fermi-liquid (nFl) ln T 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.