PHYSICAL-PROPERTIES OF COMMENSURATE DOMAINS IN THE INCOMMENSURATE PHASE

The physical properties of the long-period commensurate (LPC) ferroele ctric phase are investigated in the [N(CH3)4]2CoCl4 crystal. It is fou nd that in this phase regions of incommensuration exist. They lead to ordering of defects and impurities. It is established that the applica tion of an electric field leads to the appearance of additional peaks in the epsilon'(ij) = f(T) dependences near the phase transitions at T (c) and T'(i) on the side of the ferroelectric phase as well as to a c hange of the temperature regions of incommensurability wave vector k(c ) localization on commensurate values of higher order. The LPC phases possess the properties of both commensurate and incommensurate (IC) ph ases. Besides, they have some peculiar properties, such as splitting o f the epsilon'(ij) peak at phase transitions and double loops in the d ependence epsilon'(a) = f(E), due to the commensurate and IC region in teraction.