J. Phys. I France
Volume 5, Numéro 2, February 1995
Page(s) 235 - 244
DOI: 10.1051/jp1:1995125
J. Phys. I France 5 (1995) 235-244

High Pressure Elastic Neutron Scattering Study of the Incommensurability in ND 4DC 2O 4-1/2 D 2O (AHOD)

J. Toulouse1, R.M. Pick1 and F. Moussa2

1  Département de Recherches Physiques, Université Pierre & Marie Curie 4, place Jussieu, 75230 Paris Cedex, France
2  Laboratoire Léon Brillouin (CEA-CNRS), CE Saclay 91191 Gif-sur-Yvette Cedex, France

(Received 20 April 1994, received in final form 20 October 1994, accepted 27 October 1994)

Several exprimental studies have identified, in ND 4DC 2O 4-1/2 D 2O (AHOD), the existence of an incommensurate phase above a critical pressure, $P_{\rm c}\approx 2.6$ kbar. This phase, and the transition leading to it, has been well described by a compressible ANNNI model up to approximately 8 kbar. In order to further test the model, we have performed elastic neutron scattering measurements from 7 kbar up to 13 kbar and have followed a Bragg peak satellite as a function of temperature. The results show that, for intermediate pressures, the system remains incommensurate over a braod range of tempertures below the transition and that the $c^{\ast}/4$ and c $^{\ast}/5$ lock-in phases appear only at low tempertures. At higher pressures, the $c^{\ast}/3$ phase appears to be stable even at 0 K; the reasons for these differences with the rigid ANNNI model are discussed.

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