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(CH 3 ) 4 ) 2 CuCl 4 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.

Ferroelastic property of tetramethylammonium tetrachlorozincate tetrachlorocuprate, [N(CH3)4]2Zn1−xCuxCl4 (x = 0, 0.1, 0.3, 0.5, and 1)

“…The physical properties of [N(CH 3 ) 4 ] 2 ZnCl 4 and [N(CH 3 ) 4 ] 2 CuCl 4 have been studied using various experimental methods by several research groups. [11][12][13][14][15][16][17][18][19][20] Ribet et al 21 reported observing ferroelectric-ferroelastic phase transitions of [N(CH 3 ) 4 ] 2 ZnCl 4 through X-ray and synchrotron topography. Recently, the roles of chemically inequivalent a-N(CH 3 ) 4 and b-N(CH 3 ) 4 ions in [N(CH 3 ) 4 ] 2 ZnCl 4 and [N(CH 3 ) 4 ] 2 CuCl 4 have been reported by static nuclear magnetic resonance (NMR) and magic angle spinning (MAS) NMR, respectively.…”