Disorder-driven non-Fermi-liquid behavior inCeRhRuSi2

We report measurements of the bulk magnetic susceptibility and ${}^{29}\mathrm{Si}$ nuclear magnetic resonance (NMR) linewidth in the heavy-fermion alloy ${\mathrm{CeRhRuSi}}_2.$ The linewidth increases rapidly with decreasing temperature and reaches large values at low temperatures, which strongly suggests the wide distributions of local susceptibilities ${\chi }_j$ obtained in disorder-driven theories of non-Fermi-liquid (NFL) behavior. The NMR linewidths agree well with distribution functions $P\left(\chi \right)$ which fit bulk susceptibility and specific-heat data. The apparent return to Fermi-liquid behavior observed below 1 K is manifested in the vanishing of $P\left(\chi \right)$ as $\overrightarrow{\chi }\infty ,$ indicating the absence of strong magnetic response at low energies. Our results point out the need for an extension of some current theories of disorder-driven NFL behavior in order to incorporate this low-temperature crossover.