The effect of randomness on the quantum spin system Tl1-xKxCuCl3 with x=0.44 studied by the zero-field muon-spin-relaxation (ZF-mu SR) method

摘要

Zero-field muon-spin-relaxation (ZF-mu SR) measurements were carried out down to 80 mK on the randomness bond system Tl1-xKxCuCl3 with x = 0.44. Time spectra are well fitted by the stretched exponential function exp(- lambda t)(beta). The muon spin relaxation rate lambda increases rapidly with decreasing temperature, and beta tends to 0.5 at 80 mK. The divergent increase of lambda suggests the critical slowing down of the frequency of the Cu-3d spin fluctuations toward a spin frozen state below 80 mK, and the root-exponential-like behavior of the time spectrum indicates that the origin of the relaxation is possibly the spatially-fixed fluctuating dilute moments.