K. S. Lee

Phase transitions in layer structured (C10H21NH3)2SnCl6

Phase transitions in the quasi-two-dimensional layer structured (C10H21NH3)2SnCl6, an order–disorder transition and a conformational transition of the hydrocarbon chains, were studied by means of 1H NMR (nuclear magnetic resonance). A newly defined order parameter in the low-temperature phase, the dipolar splitting of the rigid hydrocarbon lineshape component, was shown to represent the order–disorder motion of the hydrocarbon chains, explicitly revealing its three-dimensionality. The conformational transition was marked by a discontinuity in the spin-lattice relaxation rate (1/T1). On the other hand, no obvious anomaly was observed in the spin-lattice relaxation rate at the order–disorder transition at 200 MHz, whereas a weak anomaly was observed at 45 MHz, indicating that the critical dynamics associated with the order–disorder transition is manifest in the low-frequency region of the spectral density.

Application of CRAMPS for a Phase Transition in H + -ion irradiated TlH 2 PO 4

We studied the hydrogen-bonded (TDP) ferroelectrics treated with the proton-beam bombardment. The TDP material was irradiated with 1-MeV proton beam at a dose of . In order to analyze the hydrogen environment in TDP, we carried out the high resolution nuclear magnetic resonance (NMR) - i.e., Combined Rotation And Multiple Pulse Spectroscopy (CRAMPS) measurement. The isotropic chemical shift of hydrogen indicates its displacive property is related to the lattice deformation which occurs throughout the antiferroelectric-, the ferroelastic- and the paraelastic-phase transitions. The temperature dependence of reveals the electronic charge redistribution is induced by the proton-beam irradiation and the elastic property.