BEHAVIOR OF THE OPTICAL INDICATRIX AND SMALL-ANGLE LIGHT-SCATTERING IN THE CASE OF DEVILS STAIRCASE

The deformation and rotation of the optical indicatrix and the scatter ing of light in the incommensurate phases which consist of a sequence of phases with superstructures are investigated. The periods of such s uperstructures are large but commensurate with the period of the cryst alline lattice. The values of deformation and rotation of the optical indicatrix are determined on the basis of the analysis of light passed through [N(CH3)4]2FeCl4 and [N(CH3)4]2CuCl4 crystals. The pulsing def ormation of the optical indicatrix and its rotation in the commensurat e regions are found in the incommensurate phase. It is shown that the investigated scattering of light is connected with the scattering on t he phason.