Mn 3d state of [formula omitted] studied by Mn 2p–3d resonant photoemission spectroscopy

Abstract

Pr 0.5 Ca 0.5 MnO 3− δ ( δ ∼ 0.05 ) exhibits a charge-order transition around 240 K. We have investigated the Mn 3d states of Pr 0.5 Ca 0.5 MnO 3− δ above and below the transition temperature by using valence-band photoemission spectroscopy in the Mn 2 p → 3 d photoabsorption region. We have examined the Mn 3d electronic structure of Pr 0.5 Ca 0.5 MnO 3− δ by comparing the photoemission spectra taken with photon energies well above the Mn 2p 1/2 absorption peak and below the Mn 2p absorption edge in order that the spectrum may not be influenced by particular photo-excited states at different temperatures. After the charge ordering is developed, the obtained Mn 3d spectrum clearly shows increase in intensity around 0.8 eV below the Fermi level, whereas the off-resonance photoemission spectrum shows decrease there. These indicate that the hybridization between the Mn 3d e g orbitals with oxygen 2p decreases and the 3d e g electron is localized on the Mn 3+ site when the charge ordering of Mn ions takes place and that there exists the polaron above the transition temperature.