1 H and 205 Tl Spin-Lattice Relaxation at Low Temperatures in Tl 3 H(SO 4 ) 2

Abstract

It was found from the temperature dependence of spin-lattice relaxation rates of 1 H and 205 Tl nuclei ( 1 H- T 1 m 1 and 205 Tl- T 1 m 1 ) that spin-lattice relaxations of 1 H and 205 Tl 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 Tl 3 H(SO 4 ) 2 shows the quantum mechanical process such as proton tunneling at low temperatures. The anomalous behavior of 1 H- T 1 m 1 at around 61 K indicates that proton dynamics is changed at around 61 K. Furthermore, it is suggested from the anomalies of 1 H- T 1 m 1 and 205 Tl- T 1 m 1 at around 7 K that Tl 3 H(SO 4 ) 2 shows a phase transition accompanied by the anomaly of the magnetic dipole-dipole fluctuation at around 7 K.