Investigation of Proton Dynamics in a (CH$_{3})_{4}$NCdCl$_{3}$ Single Crystal by using $^{1}$H Nuclear Magnetic Resonance Measurements

(CH$_{3})_{4}$NCdCl$_{3}$(TMCC) is reported to exhibit two first-order structural phase transitions. The crystal has a hexagonal structure in phase I at room temperature and then changes to a monoclinic one in phase II below 118 K. Finally a ferro-elastic monoclinic phase III appears below 104 K. The a- and c-axes of TMMC were found by using X-ray diffraction at room temperature. $^{1}$H NMR measurements of spectrum, spin-lattice relaxation time T$_{1}$ and rotating-frame relaxation time T$_{1\rho }$ were performed at 4.8 T parallel or perpendicular to the c-axis from 300 K down to 65 K. The spectrum shows no significant changes at both transition temperatures. T$_{1}$ and T$_{1\rho}$ monotonically decrease at low temperature and then show an abrupt decrease around 110 K. As the temperature decreases further, T$_{1}$ shows a minimum at 100 K and becomes longer whereas T$_{1\rho }$ continuously decreases. From these data, the proton dynamical behavior is analyzed and identified.