1999/12/15 by I. V. Stasyuk, Stasyuk, I. V., O. V. Velychko +1
Materials Science · Physics and Astronomy · #Condensed Matter (cond-mat) #FOS: Physical sciences #Optical and Acousto-Optic Technologies #Solid-state spectroscopy and crystallography #cond-mat
paper · pdf · doi:10.48550/arxiv.cond-mat/9912285
15 pages, LaTeX2e, 16 figures in EPS format; some theory and discussion added; submitted to Phase Transition
openalex publication_date 1999/12/15 · arxiv created 2000/02/18 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
A four-state model is proposed for description of the sequence of phase transitions in ferroelectric crystals of DMAGaS and DMAAlS type. The ordering processes in the subsystems of DMA groups are considered as a main reason of such transformations. The interaction between groups in their various orientational states is taken into account in the dipole-dipole approximation. Obtained thermodynamical characteristics of the model (spontaneous polarization, occupancy of orientational states, dielectric susceptibility, phase diagram) are in good agreement with experimental data. The experimental fact of suppression of ferroelectric phase at increase of hydrostatic pressure is explained under assumption that pressure changes the difference between energies of various orientational states of DMA groups mostly.