The ferroelastic transition of betaine borate |
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Authors: | H. -J. Zimmer Th. Hermann H. -G. Unruh |
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Affiliation: | 1. Fachbereich Physik, Universit?t des Saarlandes, D-66041, Saarbrücken, Germany
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Abstract: | The ferroelastic transition of betaine borate at about 142 K and the nonlinear temperature dependence of the corresponding critical elastic modulus are related to the softening of optical phonons. The transition has to be considered a ferroelastic one of the optic type, i.e. pseudoproper one, therefore. It is shown by Raman spectroscopic results that the transition is induced by a strong bilinear coupling between a homogeneous strain and at least two optic lattice modes which are of the same symmetry as the strain. Optic and dielectric, investigations support the second-order character of and the classical behaviour at this transition, which have been reported in the literature. Differences and similarities to the ferroelastic transition of betaine fumarate are discussed. |
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Keywords: | 62.20.D 78.30 64.70.K |
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