Fine structures in electron energy-loss spectra, observed 30-40 eV beyond the threshold of oxygen K-edges in perovskite-type manganites BiMnO3 and LaMnO3, are discussed. LaMnO3 with orthorhombic symmetry (space group Pbnm) shows a clear peak in this region. However, BiMnO3 with a heavily distorted perovskite-type structure (monoclinic, space group C2) does not show an appreciable peak. It is demonstrated that peaks in this energy region arise from the resonance effect of ejected core electrons and that the shape is sensitive to the environment of neighbouring oxygen atoms in the perovskite-type structures.
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