DETERMINATION OF THE CRYSTAL-FIELD STRENGTH IN MANGANESE COMPOUNDS BY PARALLEL ELECTRON-ENERGY-LOSS SPECTROSCOPY

The near-edge structure of the Mn L(3)-edges from several minerals containing Mn in the high-spin state is presented. The L(3)-edges from Mn(II) were recorded for minerals containing different ligands. The crystal field strength was determined from the spectra and compared to values derived from optical measurements. Minerals which contained Mn(III) in a Jahn-Teller distorted environment gave a distinctive L(3)-edge shape to which it was possible to assign orbitals based on D-4h symmetry. The Mn(IV) oxides exhibit L(3)-edges which are split into two well resolved peaks. This splitting matches that on the pre-peak of the O K-edge and corresponds to the crystal field strength.