Optical absorption and magnetic circular dichroism of MnBr2

Abstract Absorption and Magnetic Circular Dichroism spectra of MnBr 2 in the spectral region 17 000–31 000 cm -1 at temperatures between 2.3 and 250 K and for magnetic fields up to 5 T are reported. The observed bands are attributed to d-d transitions on the Mn 2+ ions. An assignment of the observed spectra is given with the aid of a parametric calculation of the energy levels. Exchange interactions between neigbouring Mn 2+ ions play a dominant role in the absorption process. The breaking of the parity and spin selection rules leads to four possible mechanisms for electric dipole d-d transitions: (A) vibronic/spin-orbit single-ion, (B) vibronic/exchange, (C) exchange/spin-orbit, and (D) fully exhange induced transitions. It could be shown from an analysis of the dependence of the spectra on temperature and magnetic field that all four mechanisms occur in MnBr 2 .