Reinvestigation of electrogyration in triglycine sulfate

The gyrotropy of triglycine sulfate at a wavelength of 633 nm was investigated theoretically and experimentally in the vicinity of the ferroelectric phase transition at 323 K. The electrogyrative signal, which consists of true electrogyration, linear electro-optic effect, and quadratic electro-optic effect, exhibits a contribution due to an optical anomaly caused by fluctuations of the order parameter. Building on the results of previous works by others in this field, the range of +/-5K of the phase transition was examined. The quadratic electro-optic rotation of the indicatrix changes sign 1.2 K above the transition temperature. The temperature dependence of the linear electro-optic component was found to be affected by a strong magnetic field of about 1 Tesla along the twofold axis.