^{27}Al Impurity-Satellite NMR and Non-Fermi-Liquid Behavior in U_{1-x}Th_xPd_2Al_3

Abstract

Non-Fermi-liquid (NFL) behavior in the f-sublattice-diluted alloy system U_{1-x}Th_xPd_2Al_3 has been studied using ^{27}Al nuclear magnetic resonance (NMR). Impurity satellites due to specific U near-neighbor configurations to ^{27}Al sites are clearly resolved in both random and field-aligned powder samples. The spatial mean Kbar and rms spread delta K of impurity satellite shifts, which are related to the mean chibar and rms spread delta chi of the inhomogeneous susceptibility, have been measured in field-aligned powders with the crystalline c axis both perpendicular and parallel to the external field. The relatively narrow lines observed at low temperatures suggest that disorder- induced inhomogeneity of the f-ion--conduction-electron hybridization is not the cause of NFL behavior in these alloys: at low temperatures the experimental values of delta chi(T)/chibar(T) are much smaller than required by disorder- driven models. This is in contrast to results in at least some alloys with disordered non-f-ion nearest neighbors to f ions ("ligand disorder"), where disorder-driven theories give good accounts of NFL behavior. Our results suggest that f-ion dilution does not produce as much inhomogeneity of the hybridization strength as substitution on ligand sites.