Investigation of local symmetry effects on the electronic structure of manganites: HexagonalYMnO3versus orthorhombicLaMnO3

Abstract

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 $\text{O}\text{ }K$- and $\text{Mn}\text{ }{L}_{2,3}$-edge x-ray-absorption spectroscopy (XAS) results of hexagonal ${\text{YMnO}}_{3}$ and orthorhombic ${\text{LaMnO}}_{3}$. ${\text{YMnO}}_{3}$, which has an unusual ${\text{MnO}}_{5}$ $({D}_{3h})$ site symmetry, exhibits remarkably different electronic structure and XAS line shape from those of ${\text{LaMnO}}_{3}$ with the conventional ${\text{MnO}}_{6}$ $({D}_{4h})$ site symmetry, despite the same ${\text{Mn}}^{3+}$ $(3{d}^{4})$ trivalent ionic state. We developed an algebraic formalism, which takes into account the crystal-field energies and hybridization strengths of the ${D}_{3h}$ $\text{Mn}\text{ }3d$ orbital in ${\text{YMnO}}_{3}$. 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 $\text{O}\text{ }K$-edge and $\text{Mn}\text{ }{L}_{2,3}$-edge spectra of both manganites. In the analyses of the $\text{O}\text{ }K$-edge spectra, we also took into account the $\text{Y}\text{ }4d$ and $\text{La}\text{ }4f/5d$ orbital states.