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Title: | 1H NMR study of molecular dynamics and phase transition in (NH4)2ZnBr4 |
Authors: | Ramesh, K. P. Devaraj, N. Vijayaraghavan, D. Ramakrishna, J. |
Keywords: | second moment spin-lattice relaxation time activation energy spin-rotation interaction phase transition reorientation |
Issue Date: | 1992 |
Publisher: | Taylor and Francis |
Citation: | Phase Transitions, 1992, Vol.37, p203-210 |
Abstract: | The proton second moment (M 2) and spin-lattice relaxation time (T 1) have been measured in (NH4)2ZnBr4 in the range 77–300 K. The room-temperature spectrum shows a structure which disappears around 243 K. The signal is strong and narrow even at 77 K. Proton T 1 shows a maximum at 263 K, caused by spin rotation interaction and decreases with decreasing temperature till 235 K, where it shows a sudden increase. Below 235 K, again it decreases and shows a slope change around 216.5 K (reported Tc ). From 216.5 K, T 1 decreases continuously without exhibiting any minimum down to 77 K. The narrow line at 77 K, and absence of a T 1 minimum down to 77 K indicate the possibility of quantum mechanical tunnelling in this system. Motional parameters such as activation energy and pre-exponential factor have been evaluated for the reorientational motion of the NH+ 4 ion. |
Description: | Restricted Access. |
URI: | http://hdl.handle.net/2289/7206 |
ISSN: | 0141-1594 1029-0338(Online) |
Alternative Location: | https://doi.org/10.1080/01411599208222898 |
Copyright: | 1992 Taylor and Francis |
Appears in Collections: | Research Papers (SCM) |
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1992phasetransi(1).pdf Restricted Access | Restricted Access. | 320.46 kB | Adobe PDF | View/Open Request a copy |
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