¹H NMR study of the phase transitions of trissarcosine calcium chloride single crystals at low temperature

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• 作者：Kyuhong Lee ; Moohee Lee ; Kwang Sei Lee and Ae Ran Lim
• 关键词：B. Crystal growth ; D. Phase transitions ; D. Nuclear magnetic resonance (NMR)
• 刊名：Journal of Physics and Chemistry of Solids
• 出版年：2005
• 期刊代码：69_00223697
• 类别：ch
• 出版时间：October 2005
• 卷：66
• 期：10
• 页码：1739-1743
• 文件大小：157 K

摘要

The ¹H NMR line-width and spin–lattice relaxation time T₁ of TSCC single crystals were studied. Variations in the temperature dependence of the spin–lattice relaxation time were observed near 65 and 130 K, indicating drastic alterations of the spin dynamics at the phase transition temperatures. The changes in the temperature dependence of T₁ near 65 and 130 K correspond to phase transitions of the crystal. The anomalous decrease in T₁ around 130 K is due to the critical slowing down of the soft mode. The abrupt change in relaxation time at 65 K is associated with a structural phase transition. The proton spin–lattice relaxation time of this crystal also has a minimum value in the vicinity of 185 K, which is governed by the reorientation of the CH₃ groups of the sarcosine molecules. From this result, we conclude that the two phase transitions at 65 and 130 K can be discerned from abrupt variations in the ¹H NMR relaxation behavior, and that ¹H nuclei play important roles in the phase transitions of the TSCC single crystal.