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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References
Unruh, H.-G., Heim, J., Hermann, Th.: Z. Phys. B97, 133 (1995)
Dvorak, V.: Ferroelectrics7, 1 (1974)
Aizu, K.: J. Phys. Chem. Solids,32, 1959 (1971)
Haussühl, S.: Solid State Commun.68, 963 (1988)
Haussühl, S.: Solid State Commun.50, 63 (1984)
Aizu, K.: J. Phys. Soc. Jpn,27, 387 (1969)
Sapriel, J.: Phys. Rev. B12, 5128 (1975)
Zobetz, E., Preisinger, A.: Monatshefte Chemie120, 291 (1989)
Aizu, K.: J. Phys. Soc. Jpn.28, 706 (1970)
David, W.I.F., Wood, I.G.: J. Phys. C. Solid State Phys.16, 5149 (1983)
Krummeck, H., Knorr, K., Haussühl, S.: J. Phys.: Condens. Matter6, L111 (1994)
Pinczuk, A., Welber, B., Dacol, F.H.: Solid State Commun.29, 515 (1979)
David, W.I.F.: J. Phys. C. Solid State Phys.16, 5093 (1983)
Aubry, S., Pick, R.: J. Physique32, 657 (1971)
David, W.I.F.: J. Phys. C. Solid State Phys.16, 2455 (1983)
Cowley, R.A.: Phys. Rev B13, 4877 (1976)
Zobetz, E.: (private communication)