Ammonium-ion reorientation and ordering in ND4ReO4 studied by deuteron NMR



: Vuorimaki AH, Ylinen EE

Publisher: ELSEVIER SCIENCE BV

: 1996

Physica B: Condensed Matter

PHYSICA B

: PHYSICA B

: 225

: 1-2

: 121

: 124

: 4

: 0921-4526

DOI: https://doi.org/10.1016/0921-4526(95)00235-9


The spin-lattice relaxation time T-1 and the NMR absorption line shape of deuterons in ND4ReO4 were measured in the temperature range from 46 to 294 K. The T-1 versus T curve shows a single minimum and gives the activation energy of 10.5 kJ/mol for the reorientation of the ND4 ion. Above 56 K, the absorption line is averaged by the reorientation, but remains slightly split. The residual splitting decreases in two steps with increasing temperature to a minimum at 110 K, then increases and finally diminishes near the room temperature. The results suggest that the reorientation has no preferred axis and that the ion favours one of the two equilibrium configurations this crystal provides for it.



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