Determination of electronic band structures of CaMnO3 and LaMnO3 using optical-conductivity analyses

Reflectivity spectra of CaMnO3 and LaMnO3 were measured in a wide photon energy region between 5 meV and 30 eV at room temperature. Using the conductivity spectra obtained from the Kramers-Kronig analysis, electronic structures of the manganese oxides were investigated. In particular, the states near the Fermi energy E-F, O 2p and Mn 3d (e(g),t(2g)), were studied in detail. It was found that the O 2p band is located closer to E-F than the Mn t(2g) band. For LaMnO3, the filled Mn e(g up arrow)(1) band is located closer to E-F than any other valence band. The t(2g)-e(g) Hund exchange energy was found to be about 3.4 eV and the Jahn-Teller stabilization energy E-0 was estimated to be less than 0.5 eV.