Title: DIELECTRIC RELAXATION AND FREEZING EFFECT IN SN$_2$P$_2$S$_6$
Author(s): M.M.Maior, Sh.B.Molnar, V.T.Vrabel, M.I.Gurzan, S.F.Motrja, Yu.M.Vysochanskii (Institute for Solid State Physics and Chemistry, Uzhgorod National University, Uzhgorod, Ukraine)

The temperature-frequency studies of dielectric susceptibility in Sn$_2$P$_2$S$_6$, Sn$_2$P$_2$Se$_6$, (Pb$_y$Sn$_{1-y}$)$_2$P$_2$Se$_6$ and crystals at low temperatures are reported. The freezing relaxation dynamics has been observed in a temperature-frequency dependence of the dielectric properties in the crystals which are in a polydomain ferroelectric state as well as in the crystals (Pb$_y$Sn$_{1-y}$)$_2$P$_2$Se$_6$ with $y>0.4$ which at low temperatures are in the incommensurate phase. The nature of the effect and its interrelation with dynamics of ferroelectric domain walls and incommensurate structure is discussed.

Key words: domain walls, freezing effect, dielectric properties
PACS:77.84.D, 77.80.Bh