Ferroelectric Phase Transition in Ammonium Hydrogen Bis (Chloroacetate). V. Nuclear Magnetic Resonance of NH4H(CH2ClCOO)2 and ND4D(CH2ClCOO)2
1981 年 50 巻 6 号 p. 2014-2021
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1981 年 50 巻 6 号 p. 2014-2021
Proton resonance line shape and spin-lattice relaxation time T1 were measured for polycrystalline NH4H(CH2ClCOO)2 in ferro- and para-electric phases. Peculiar line shape and its temperature variation were ascribed to increasing tunnel splitting between the A and T symmetry levels in the librational ground state of NH4+ ion from 15 kHz at 23 K to 20 kHz at 60 K. This increase corresponds to a decrease of rotational potential barrier (14.6 kJ mol−1 at 0 K) and a decrease of the ferroelectric order. Deuteron resonance line shape and T1 were also measured for polycrystalline ND4D(CH2ClCOO)2. An extra line-width below Tc was proportional to (Tc−T)0.76±0.09. An activation energy of NH4+ and ND4+ reorientation above the transition point, 10.9 kJ mol−1, was deduced from the T1 data.
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