35Cl NQR Spin-Lattice Relaxation in Paramagnetic CuPtCl6 · 6H2O

Abstract

Abstract 35Cl NQR spin-lattice relaxation times T1Q of paramagnetic CuPtCl6 · 6H2O were measured as a function of temperature. Below the cooperative Jahn-Teller phase transition at Tc = 136 K, an almost temperature independent T1Q between 0.6 and 1 ms was obtained for each line of the triplet observed. This suggests that the nuclear spin-lattice relaxation of chlorine is dominantly determined by magnetic dipolar interactions between chlorine nuclei and electron spins. No marked anomaly in the nuclear relaxation rate was detected at T c . Above Tc , T1Q for the single 35Cl NQR line increased from 0.6 ms at Tc to 1-4 ms at 365 K. The rapid T 1Q decrease observed above ca. 390 K can be attributed to a reorientational motion of the [PtCl6]2- anion with an activation energy of 1.1 x 102 kJ mol-1 .