Verlauf der Doppelbrechung bei den Phasenübergängen II–III und III–IV von NH4Br und ND4Br*

Abstract

A method for the measurement of optical birefringence at the phase transitions of materials exhibiting domain structures is described. Moreover, the order parameter for the order-disorder-transition between phase III and II of NH4Br is derived from measuring the optical birefringence. The hysteresis of the phase transition in ND4Br and the phenomena accompanying the transition to phase IV in NH4Br are also investigated.