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

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 Tc. 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 T1Q 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 × 102 kJ mol−1. © 1990, Verlag der Zeitschrift für Naturforschung. All rights reserved.