Temperature dependent electron-phonon coupling in FeCl2observed by Raman scattering

Abstract

Strong coupling between an electronic transition in the ⁵T_2g(⁵D) manifold of Fe²⁺ ions in FeCl₂ and the E_g optical phonons in this material has been observed by light scattering. The Raman spectrum is temperature dependent and shows a marked change at the antiferromagnetic ordering temperature. Above T_N, the spectrum contains a symmetric band which becomes asymmetric on the high energy shoulder when the temperature is lowered. Just below T_N the band comprises two sharp features accompanied by a third broad band. Well below T_N the sharp features have coalesced. A simple model is presented which successfully accounts for the observed temperature dependence of the band position, width and structure.