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NMR studies of phase transition in ammonium hydrogen bischloroacetate, NH4H(CH2ClCOOO)2

Sundaram, CS and Shenoy, RK and Ramakrishna, J and Chandrasekhar, K and Sastry, VSS (1984) NMR studies of phase transition in ammonium hydrogen bischloroacetate, NH4H(CH2ClCOOO)2. In: Ferroelectrics, 61 (1). 233 -239.

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Proton second moment (M2) and spin-lattice relaxation time (T1) of Ammonium Hydrogen Bischloroacetate (ABCA) have been measured in the range 77-350 K. A value of 6.5 G2 has been observed for the second moment at room temperature, which is typical of NH4+ reorientation and also a second moment transition in the range 170-145 K indicates the freezing of NH4+ motion. The NMR signal disappears dicontinuously at 128 K. Proton spin-lattice relaxation time (T1) Vs temperature, yielded only one sharp miniumum of 1.9 msec which is again typical of NH4+ reorientation. A slope change at 250 K is also observed, prbably due to CH2 motion. Further, the FID signal disappears at 128 K. Thus the Tc appears to be 128 K (of two reported values 120 K and 128 K). Activation energies have been calculated and the mechanism of the phase transition is discussed.

Item Type: Journal Article
Publication: Ferroelectrics
Publisher: Taylor and Francis Group
Additional Information: Copy right of this article belongs to Taylor and Francis Group.
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 27 Nov 2009 07:55
Last Modified: 27 Nov 2009 07:55
URI: http://eprints.iisc.ac.in/id/eprint/21859

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