1H NMR study of molecular dynamics and phase transition in (NH4)2ZnBr4

Please use this identifier to cite or link to this item: http://hdl.handle.net/2289/7206

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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