Title: THE INFLUENCE OF DEFECTS AND CONDUCTIVITY ON THE DOMAIN STRUCTURE PROPERTIES AND THE MEMORY EFFECT IN THE FERROELECTRICS-SEMICONDUCTORS Sn_2P_2Se_6
Authors: Yu.M.Vysochanskii, A.A.Molnar, M.M.Khoma, S.F.Motrja (Institute of Solid State Physics and Chemistry Uzhgorod University, 46 Pidgirna Str., 294000 Uzhgorod, Ukraine)

For the proper uniaxial ferroelectrics Sn$_2$P$_2$Se$_6$ with the controlled content of different type of impurities the investigations of dielectric permeability temperature dependence are performed with the aim to determine the influence of the crystal structure defects upon: the efficiency of the thermal memory effect recording in the incommensurate (IC) phase; the second order phase transition (PT) from the paraelectric phase to the IC phase at temperature T$_i$ and upon the first order PT from IC phase to ferroelectric phase at temperature T$_{\rm c}$; the anomalous hysteresis of the dielectric properties temperature dependence in the IC phase; the dielectric contribution of the domain walls in the ferroelectric phase. Static defects smear the anomaly at the PT from paraelectric phase to IC phase, increase the anomalous hysteresis in the IC phase and the hysteresis of the lock-in transition temperature T$_{\rm c}$, suppress the dielectric contribution of domain walls in the ferroelectric phase and destroy the memory effect in the IC phase. The increase of the charge carrier concentration also suppresses the dielectric output of the domain walls in the ferroelectric phase but at the same time it supports a more clear memory recording in the IC phase. Such a tendency agrees with the estimations in the mean-field approximation for the characteristics of a domain structure in the ferroelectric phase and memory effect in the IC phase in the ferroelectrics-semiconductors investigated.

Comments: Figs. 8, Refs. 24, Tabs. 0.