Kondo disorder and non-Fermi-liquid behavior in UCu5-xPdx and CeCu5.9Au0.1

Muon spin rotation (mu SR) has been used to probe non-Fermi-liquid (NFL) behavior in the heavy-fermion alloys UCu5-xPdx, x = 1.0 and 1.5, and CeCu5.9Au0.1 Zero-field mu SR puts an upper bound of similar to 0.01 mu(B)/U atom on any static magnetism in UCu5-xPdx, which is too weak to affect the transverse-field mu SR linewidth or to give rise to NFL behavior. In agreement with NMR results, mu SR spectra in transverse fields suggest that a broad distribution of Kondo temperatures (''Kondo disorder'') is important in UCu5-xPdx. NFL anomalies at temperature T then arise from ''free'' spins for which T-K much less than T. Comparison of mu SR and NMR linewidths also indicates short-range spatial correlation of the Kondo disorder in UCu5-xPdx, in agreement with the local character of the dynamic susceptibility inferred from neutron scattering experiments. In CeCu5.9Au0.1 the data suggest significant Kondo disorder only if the spatial correlation is long ranged, which is not indicated by other properties of this alloy.