TEMPERATURE DEPENDENCE OF THE BRILLOUIN SPECTRA IN Sn2P2S(Se)6 FERROELECTRIC CRYSTALS

Condensed Matter Physics

关键词: Brillouin scattering;    soft mode;    ferroelectrics;    Lifshitz point;   

DOI  :  10.5488/CMP.6.2.315

来源: DOAJ

【 摘 要 】

A temperature dependence of hypersound velocities at transition from a paraelectric phase to ferroelectric phase in Sn₂P₂S₆ crystals was investigated by Brillouin scattering spectroscopy. Based on these data, full set of elastic constants was determined. Similar measurements were also performed for Sn₂P₂(Se_0.28S_0.72)₆ mixed crystals in the paraelectric phase near a Lifshitz point. The sound velocity indicatrices' evolution at transition from Sn₂P₂S₆ to Sn₂P₂(Se_0.28S_0.72)₆ was observed and softening of transverse acoustic phonons in the paraelectric phase near the Lifshitz point was found. An instability of the acoustic phonons is induced by an interaction with a soft optic mode which is the origin of an incommensurate phase appearance in mixed crystals Sn₂P₂(Se_xS_1-x)₆ with x > x_LP=0.28.

【 授权许可】

Unknown