Muon spin relaxation study of spin-glass freezing in the Heusler compound Ru_1.9Fe_0.1CrSi

In the temperature dependence of magnetization, the Heusler compound Ru_1.9Fe_0.1CrSi exhibits a peak at a temperature which is defined as TN*. Below that temperature strong irreversibility occurs, the onset temperature of which is defined as T_g. However, no evidence of long-range order has been found. In this study the magnetic properties of these anomalies were investigated using zero-field (ZF) and longitudinal-magnetic- field (LF) muon-spin-relaxation (μSR) measurements. In the temperature dependence of the relaxation rate of ZF-μSR, a peak at ∼16 K was observed, which agrees with T_g. LF-μSR measurements as a function of magnetic field reveal the existence of a static internal magnetic field at 0.3 K. Around TN*∼30 K, we detected no anomalies that can be associated with a magnetic phase transition in the temperature dependence of the relaxation rate of μSR, but a large decrease in the initial asymmetry was observed. LF-μSR measurements suggest that the internal magnetic field appears even around TN*. These results suggest that around TN* independent spin-frozen regions form inhomogeneously. With decreasing temperature these regions gradually develop, and eventually, at T_g spin-glass freezing occurs with correlations over the whole sample.