Optical and X-ray studies on phase transition of (NH4)2SO4

Abstract Temperature and biasing electric field dependences of a gyration tensor component g 12, of ammoniumu sulfate were measured by using the high accuracy universal polarimeter, HAUP, together with birefringences. g 12, was found to appear abruptly at the Curie point and to keep the constant value irrespective of change of the temperature. The x-rays two-dimensional method was applied for measuring the lattice strains from 300K down to 6K.