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.

The field dependence of the ωSR relaxation function in YbBiPt, together with an anisotropic resistive anomaly recently discovered by Movshovich et al., indicate that both the Yb ions and the conduction electrons undergo magnetic ordering. New evidence is also presented for a change in Yb spin-ordering or spin-dynamics below about 0.1 K. © 1994.

Zero-field muon spin relaxation studies are reported for crystalline YbxY1-xBiPt for x = 1.0 and 0.5. YbBiPt exhibits an extremely large Cp/T ratio y ≅ 8J/(K2 mol Yb) below T ≅ 0.2 K and shows evidence for some type of magnetic order below 0.4 K from χAC. The μSR data are consistent with a highly frustrated spin system segmented into two types of magnetic domains, one of which freezes into a disordered state below Tf ≅ 0.4-0.5 K at a temperature relatively independent of the Yb concentration. The frozen spin moment of ∼0.1μB is highly reduced from the high temperature free-ion value, and is independent of the Yb concentration. © 1993.