Glassy Spin Dynamics in Non-Fermi-Liquid UCu_{5-x}Pd_x, x = 1.0 and 1.5
  Local f-electron spin dynamics in the non-Fermi-liquid heavy-fermion alloys UCu_{5-x}Pd_x, x = 1.0 and 1.5, have been studied using muon spin-lattice relaxation. The sample-averaged asymmetry function Gbar(t) indicates strongly inhomogeneous spin fluctuations, and exhibits the scaling Gbar(t,H) = Gbar(t/H^\gamma) expected from glassy dynamics. At 0.05 K \gamma(x=1.0) = 0.35 \pm 0.1, but \gamma(x=1.5) = 0.7 \pm 0.1. This is in contrast to inelastic neutron scattering results, which yield \gamma = 0.33 for both concentrations. There is no sign of static magnetism \gtrsim 10^{-3} \mu_B/U ion in either material above 0.05 K. Our results strongy suggest that both alloys are quantum spin glasses. 
D. E. MacLaughlin (1), O. O. Bernal (2), R. H. Heffner (3), G. J.   Nieuwenhuys (4), M. S. Rose (1), J. E. Sonier (3), B. An...