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In this work we present a detailed study of the temperature evolution (290 K–20 K) of the polarized Raman spectra in a single crystal of glycinium phosphite. The phase transition manifests itself by the activation of new Raman bands and by the occurrence of anomalies in the temperature dependence of the wavenumber of some external and internal modes. The results show that occurring deformations in molecular units contribute relevantly to the spontaneous polarization in GPI. The anomalous behaviour of the wavenumber and of the damping constant of some bands is in good agreement with a theoretical model based in a pseudospin-phonon interaction. [ABSTRACT FROM AUTHOR]

The mixed system of betaine arsenate and betaine phosphate (BP)x(BA)1-x displays, at low temperatures, dielectric anomalies that have been tentatively associated to re-entrant glass phases. In this work, we report results obtained for the composition x = 0.52. The temperature dependence of the complex dielectric constant, polarization hysteresis loops and pyroelectric currents reported prove that an effective ergodicity breaking occurs in the antiferroelectric phase and show that this phase is destabilized at low temperatures. There is also evidence for a high internal bias field, in the whole temperature range studied. Infrared and Raman spectroscopy indicate that the various dielectric anomalies observed reflect structural transformations. [ABSTRACT FROM AUTHOR]

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]