Ferroelectric Phase in Betaine Phosphite Studied by Raman Scattering.

In this work we present a detailed study of the temperature dependence (35 K- 290 K) of the Raman spectra in a single crystal of betaine phosphite. A softening of a relaxational mode is observed above and below the para-ferroelectric phase transition at Tc2 ∼ 213 K, which appears to have its primary origin in the different internal dynamic deformations and reorientations of molecular units. Our results suggest the existence of a certain degree of local disorder between 110 K and 170 K. [ABSTRACT FROM AUTHOR]