Optical investigations in [N(CH3)4]2MnCl4

Abstract
Some optical investigations including measurements of birefringence and angle between the extinction positions in different domains, have been performed on [N(CH3)4]2MnCl4, In addition the domain structure has been studied using an optical microscope. The observed anomalies in the birefringence measurements clearly confirm the existence of an incommensurate phase in a temperature interval of 0.6°C.