Deflection and diffraction of light by ferroelastic crystals of sodium-ammonium tartrate tetrahydrate and lithium-ammonium tartrate monohydrate

Abstract

Deflection of light by domains in ferroelectric-ferroelastic crystals of NaNH₄C₄H₄O₆* 4H₂O and Li-NH₄C₄H₄O₆* H₂O has been studied. Angular relations between the incident light beam and deflected beams were measured and interpreted on the basis of crystal optics. For the first time light diffraction was observed in the direction along which the adjacent domains did not show differences in optical anisotropy. The role of domain walls in formation of diffraction pattern as well as the polarization of deflected beams were discussed.

For lithium-ammonium tartrate crystals a simple relation between the deflected beam intensity and the spontaneous shear strain X_5s , was found.