μsR Study of Kapellasite-type Quantum Kagome Antiferromagnet CaCu3(OH)6Cl2·0.6H2O

Abstract

To elucidate the dynamical properties of quantum kagome antiferromagnet CaCu3(OH)6Cl2·0.6H2O, we performed muon spin rotation and relaxation (μSR) experiments on polycrystalline and single crystalline samples down to 82 mK. The internal magnetic field estimated from zero-field (ZF) μSR develops in the magnetic ordered phase below T∗= 7.2 K. Remarkably, ZF-μSR spectra below the transition temperature exhibit a relaxation over a long-time, suggesting that persistent spin fluctuations exist in the magnetic ordered phase. The transverse relaxation rate monotonously saturates below T∗, while the longitudinal relaxation rate decreases below 1K with temperature-square power dependence. This implies that a change in the fluctuation mode occurs which can be detected by μSR with a characteristic time window.