Elasticity of lyotropic chromonic liquid crystal Sunset Yellow probed by magnetic Frederiks transition*

By using director reorientation in the magnetic field, we determine the concentration and temperature dependencies of the splay $K_1$, twist $K_2$, and bend $K_3$ elastic constants (normalized by the anisotropy of the diamagnetic susceptibility) for a nematic lyotropic chromonic liquid crystal (LCLC) Sunset Yellow. In a sharp contrast to thermotropic liquid crystals, the Frederiks effects in LCLC show a hysteresis, which is more pronounced at high concentration and low temperatures. We attribute the hysteresis to the changes in self-assembled structure of LCLC aggregates under the influence of field-imposed deformations.