Electronic absorption spectra of KMnF3, RbMnF3, and MnF2

Abstract

The absorption spectra of KMnF3 and RbMnF3 in the region 17000-47000 cm-l are reported in detail for room temperature and 20�K. Excellent agreement between experiment and a ligand field calculation using the free atom representation is obtained for the bands with energy less than 35000 cm-l. The analysis of the bands with energy greater than this requires an explanation involving the simultaneous excitation of pairs of manganese ions, and consistent assignments of these bands for the spectra of KMnF3, RbMnF3, and MnF2 are given. The relative order of the 4A1g and 4Ega states is established, and a theoretical argument to support this uses differences in inter-electronic repulsion energies for the 4Ega; and 4Egb states. The theoretical line shapes for the magnon-exciton bands of MnF2 at 25000 cm-1 are compared with the observed shapes.