Eur. Phys. J. B 3, 7-15 (1998)
https://doi.org/10.1007/s100510050278

Brillouin scattering study of transverse elastic waves in the α, incommensurate and β phases of AlPO4

¹ Centre de Recherches sur la Physique des Hautes Températures, Centre National de la Recherche Scientifique, 45071 Orléans, France and Université d'Orléans, 45067 Orléans, France
² Laboratoire de Physicochimie de la Matière Condensée, Centre National de la Recherche Scientifique, 34095 Montpellier, France and Université de Montpellier II, 34095 Montpellier, France

Corresponding author: ^a magneron@admin.cnrs-orleans.fr

Received: 2 October 1997
Revised: 3 December 1997
Accepted: 29 January 1998
Published online: 15 May 1998

Abstract

Transverse and pseudo-transverse elastic waves have been studied in several scattering geometries in order to investigate the temperature dependences of and over the range 300-1100 K, including the transitions near 860 K. These results complete those on we have obtained in a previous work. All these constants display discontinuities at the lock-in transition. In the α phase, the results are analysed in term of lowest order couplings between strains (e) and the order parameter (Q). The main features are described by the lowest order biquadratic coupling, in particular for in a large temperature range. However, it appears that a contribution of the next coupling term arises for below  K and that the first two lowest order terms have to be taken into account even just below the lock-in transition in the case of . The temperature dependence of Q has been deduced and it can be well described in the framework of Landau's theory.