J. Phys. I France
Volume 3, Numéro 12, December 1993
Page(s) 2437 - 2449
DOI: 10.1051/jp1:1993255
J. Phys. I France 3 (1993) 2437-2449

35Cl NQR and calorimetric reinvestigation of the incommensurate phase of bis(4-chlorophenyl) sulfone : evidence for no lock-in transition

J. Etrillard1, B. Toudic1, M. Bertault1, J. Even1, M. Gourdji2, A. Péneau2 and L. Guibé2

1  Groupe Matière Condensée et Matériaux, U.R.A. au C.N.R.S. 040804, Université de Rennes I, Bâtiment B11, Campus de Beaulieu, 35042 Rennes Cedex, France
2  Institut d'Electronique Fondamentale, U.R.A. au C.N.R.S. 0022, Université Paris XI, Bâtiment 220, 91405 Orsay Cedex, France

(Received 8 March 1993, accepted in final form 3 August 1993)

35Cl NQR and calorimetric measurements in BCPS have been reinvestigated between 77 K and room temperature (NQR) and between 100 K and 180 K ( $C_{\rm P}$). It is shown that, in contradiction with conclusions found in literature, there is no lock-in transition at 115 K. These new results are in agreement with those obtained with other experimental techniques: Raman scattering, X-ray diffraction, neutron diffraction and proton NMR; the latter indicate that the incommensurate phase, appearing on cooling at 150 K, persists down to 4.2 K, at least. The shape of the 35Cl NQR spectrum in the BCPS incommensurate phase shows that the frequency of a chlorine nucleus is a function of the order parameter, through linear and quadratic terms.

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