Physical properties and phase transition of tetragonal X2CuT4 · 2Q2O, X = K, Rb, NH4, ND4, T = C1, Br, Q = H, D

Abstract

Abstract Refractive indices, Faraday effect, dielectric constants, and elastic constants have been studied on crystals grown from aqueous solutions. The physical properties are closely related to the chemical composition of the crystals. In the ammonium salts the first transition cycle of a virgin crystal yields a different behaviour compared to subsequent cycles. Copper salts and the isotypic manganese compound exhibit transitions of different type. The transition temperature is correlated to the void occupied by the [NH4]+-ions.