Investigation of local symmetry effects on the electronic structure of manganites: Hexagonal YMnO₃ versus orthorhombic LaMnO₃

The local site symmetry effects on electronic structure of manganites were investigated by using theoretical analyses in terms of the cluster model calculations for the OK - and Mn L2,3 -edge x-ray-absorption spectroscopy (XAS) results of hexagonal YMnO3 and orthorhombic LaMnO3. YMnO3, which has an unusual MnO5 (D3h) site symmetry, exhibits remarkably different electronic structure and XAS line shape from those of LaMnO3 with the conventional MnO6 (D4h) site symmetry, despite the same Mn3+ (3 d4) trivalent ionic state. We developed an algebraic formalism, which takes into account the crystal-field energies and hybridization strengths of the D3h Mn3d orbital in YMnO3. The deduced values are very consistent with the first-principles local-density approximation plus Hubbard U calculation results. The cluster model calculations involving the different site symmetries well reproduce the OK -edge and Mn L2,3 -edge spectra of both manganites. In the analyses of the OK -edge spectra, we also took into account the Y4d and La4f/5d orbital states.