Divalent manganese in an axial symmetry site of additively coloured CaO single crystals

Abstract

Electron paramagnetic resonance data dealing with the first observation of a Mn2+ axial center in CaO are reported. The tetragonal EPR spectrum was found in additively coloured crystals at 100K the best-fit parameters to the spin-Hamiltonian were found to be : g/sub ///=2.0015 (5), gperpendicular to =2.0020 (5), b20=+132.6 (4)*10-4 cm-1, b40=+3.5 (3)*10-4 cm-1, b44=+11.7 (8)*10-4 cm-1, and A=-67.2 (5)*10-4 cm-1. The hyperfine coupling constant is anomalously small and points towards a considerable covalent bonding. The analysis of the data presented in this paper strongly suggests that the axial spectrum is due to Mn2+ ions perturbed by an adjacent F centre. Assuming this model, the reduction in the value of the hyperfine interaction relative to that of the free ion was estimated in terms of the approach of Simanek and Sroubek which puts the main emphasis of such a reduction on the covalent effects of the 4s orbitals of the Mn2+ ion and the result compares reasonably well with the experimental determination.