The relaxation phenomenon in proper uniaxial ferroelectric-semiconductor crystals Sn2P2S(Se)6 with incommensurate phase

Abstract

For ferroelectric-semiconductor crystals Sn2P2S(Se)6 the relaxation of electron subsystem determines the Lifshitz point shift on the phase diagram and the pinning of order parameter wave (memory e ect) in the incommensurate phase. For these proper uniaxial ferroelectrics both e ects are agreeably described by the phenomenological model, which assumes: the renormalization of the spatial dispersion of the sti ness coe cient for the order parameter uctuations due to the relaxational variation of the charge carriers concentration on the impurity energy level in the forbidden band of the crystal; the local centres energy modulation, caused by the non-uniform static field of the order parameter in the IC-phase leading to the appearance of concentration-wave of the charge carriers.