Charge ordering in Bi1-xCaxMnO3 (x >= 0.75) studied by electron-energy-loss spectroscopy

The effect of charge ordering of Mn3+ and Mn4+ ions on bonding features bet ween oxygen 2p and manganese 3d orbitals in Bi1-xCaxMnO3 (x greater than or equal to 0.75) was studied along with the oxygen K edge by electron-energy loss spectroscopy. A peak at 529 eV in the oxygen K edge was found to be se nsitive to the manganese e(g) hole content via strong hybridization between oxygen 2p and manganese 3d orbitals. It was demonstrated that the intensit y was slightly reduced with the charge ordering in Bi0.2Ca0.8MnO3. This eff ect was rationalized by considering such a mechanism that the strong hybrid ization with manganese 3d orbital was weakened as a result of the lattice d istortion caused by the charge ordering, which was detected by a precise el ectron-diffraction method with energy-filtering and imaging plates. [S0163- 1829(99)05509-5].