UC Irvine

Positive-muon (μ+) spin-relaxation experiments have been carried out in a pressed-powder sample of the low-carrier-density heavy-electron system YbBiPt. Spatially inhomogeneous and disordered static Yb magnetism is observed below ∼0.5 K, with a strongly reduced Yb moment of ∼0.1μB over ∼50% of the sample volume at T=0.06 K. Substantial μ+ spin-lattice relaxation, rarely observed in heavy-electron systems, suggests anomalously slow Yb spin fluctuations. Our data are reminiscent of μ+ behavior in spin glasses, and raise the question of whether the large low-temperature specific heat in YbBiPt is due in part to low-lying magnetic excitations. © 1992 The American Physical Society.