Manifestations of Phase Transitions and the Thermooptical-Memory Effect in the Absorption Spectra of (N(CH3)4)2CuCl4 Crystals

Abstract

The manifestations of phase transitions and the spatial modulation of the structure of the (N(CH3)4)2CuCl4 crystal in its absorption spectra have been investigated. It has been established that the thermooptical-memory effect manifesting itself in the absorption spectra of this crystal entirely corresponds to the model of ordering of defects and impurities in a sample with a modulated structure. It is shown that, as a result of stabilization of the crystal studied in the incommensurate phase, its symmetry and the symmetry of the metal-halogen complex in it lower depending on the defect wave. This manifests itself as a marked shift of the intraionic-absorption bands and an increase in their intensity.