ZERO-FIELD MUON SPIN RELAXATION STUDIES OF LOW-TEMPERATURE MAGNETISM IN YBXY1-XBIPT (X = 1.0 AND 0.5)

Zero-field muon spin relaxation studies are reported for crystalline YbxY1-xBiPt for x = 1.0 and 0.5. YbBiPt exhibits an extremely large C(p)/T ratio gamma congruent-to 8J/(K2 mol Yb) below T congruent-to 0.2K and shows evidence for some type of magnetic order below 0.4 K from chi(AC). The muSR 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 T(f) congruent-to 0.4-0.5 K at a temperature relatively independent of the Yb concentration. The frozen spin moment of approximately 0.1mu(B) is highly reduced from the high temperature free-ion value, and is independent of the Yb concentration.