1H and 205Tl spin-lattice relaxation at low temperatures in Tl3H(SO4)2

It was found from the temperature dependence of spin-lattice relaxation rates of H-1 and Tl-205 nuclei (H-1-T-1(-1) and Tl-205-T-1(-1)) that spin-lattice relaxations of H-1 and Tl-205 result from a magnetic dipole-dipole relaxation. It was also found from the analysis of T-1's that the energy for the flip-flop motion of protons from O...H-O to O-H...O becomes 2.0 meV at low temperatures. These results suggest that Tl3H(SO4)(2) shows the quantum mechanical process such as proton tunneling at low temperatures. The anomalous behavior of H-1-T-1(-1) at around 61 K indicates that proton dynamics is changed at around 61 K. Furthermore, it is suggested from the anomalies of H-1-T-1(-1) and Tl-205-T-1(-1) at around 7 K that Tl3H(SO4)(2) shows a phase transition accompanied by the anomaly of the magnetic dipole-dipole fluctuation at around 7 K.