Charge-ordered state in single-crystalline CaFeO3 thin film studied by x-ray anomalous diffraction

X-ray anomalous diffraction, together with a band-structure calculation, was employed to obtain a quantitative understanding of the charge-ordering state in a single-crystalline CaFeO3 thin film. The experimental result shows a characteristic energy dispersion of the nearly inhibited reflection at 150 K, implying Fe atoms split into two distinct states. The energy dispersion is in good agreement with the calculated spectrum based on the LDA+U scheme. The calculation also reveals an electronic structure of the system where holes in the oxygen orbital surround one of the distinct Fe atoms, in spite of the total electron number in both Fe atoms remaining unchanged.