Spin-liquid-like ground states in the double hydroxyperovskites CuSn(OD)6 and MnSn(OD)6 evidenced by μSR spectroscopy

Double hydroxide perovskites with magnetic transition-metal ions were recently identified as a unique class of materials that combine magnetic frustration with correlated proton disorder—a prerequisite for quantum-disordered fluctuating magnetic ground states resembling spin liquids. Here we present the results of muon spin relaxation (μSR) measurements carried out on fully deuterated samples of the double hydroxyperovskites CuSn(OH)6 (S = 1/2) and MnSn(OH)6 (S = 5/2) over the temperature range 0.053–50 K. The absence of any long-range magnetic order is confirmed down to 0.053 K. We observe no oscillations of the muon asymmetry down to the lowest temperature. The muon relaxation rates show a continuous increase with decreasing temperature, indicating persistent spin fluctuations in both compounds. Spin correlations are consistent with homogeneous spin dynamics. These observations reinforce the assertion that both compounds have a quantum-dynamic magnetic ground state that is consistent with a spin-liquid-like phase stabilized by proton disorder.