Raman Scattering Study on Rb₂ZnBr₄

Abstract

Raman spectra of Rb₂ZnBr₄ were measured in the temperature region including the normal-incommensurate (T_i=73°C) and incommensurate-commensurate (T_c=−86°C) phase transition points. At the optical geometries of c(aa)b and a(cc)b, a soft mode has been observed whose frequency shift decreases as T_i is approached from below. At the geometry of a(ca)b, the change in the Rayleigh wing has been observed on passing. through T_c. Detailed measurements with an I₂-filter were also made.