Electrical and optical measurements on nickel iodine boracite

Abstract
Measurements of resistivity, spontaneous polarization, pyroelec. coeff., piezoelectricity, dielec. const., spontaneous Faraday rotation, spontaneous birefringence and optical rotation with temp. are reported. Between 4 and 61.5 K a single ferroelec./ferromagnetic/ferroelastic phase, consistent with Shubnikov point symmetry m', exists