Spectral studies of the structural deformation of CsMnCI3 and [NH3(CH2)2NH3]MnCI4 antiferromagnetic crystals in the vicinity of self-localized excitons
Abstract
The fine structure of optical luminescence spectra and its excitations in NH3(CH2)2NH3MnCl4 and CsMnCl3 antiferromagnetic crystals have been studied in the temperature range 4.2−20.4° K. The luminescence spectrum of these compounds has been found to display anomalously large splitting (large compared to excitation spectra) of the 4Γ4(4G)⇄6Γ1(6S) transition band. The degeneracy of the lowest excited electron state is shown to be lifted as a result of the departure of the Mn–Cl structure from a regular octahedron. The considerable increase of the splitting in the luminescence spectrum as compared to the excitation spectrum is attributable to an intensification of trigonal and orthorhombic distortions as a consequence of exciton self-localization.