It is known that dielectric non-linearity of liquid crystals (LC) is based on reorientation of their molecules (which are characterized by geometric anisometry, accompanied by anisotropy of dielectric permittivity s and magnetic susceptibility %) under external electro- and magnetostatic fields. The effective values of ε measured in specific experimental conditions can vary within the range limited by two extreme values corresponding to molecular orientations parallel and perpendicular to the external field (dielectric anisotropy Δε = ε+∥ — ε_⊥). Correspondingly, birefringence An= — ni is observed in the optical range.
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