We report experimental evidence for the charge-orbital ordering in magnetite below the Verwey transition temperature T(V). Measurements of O K-edge resonant x-ray scattering on magnetite reveal that the O 2p states in the vicinity of the Fermi level exhibit a charge-orbital ordering along the c axis with a spatial periodicity of the doubled lattice parameter of the undistorted cubic phase. Such a charge-orbital ordering vanishes abruptly above T(V) and exhibits a thermal hysteresis, correlating closely with the Verwey transition in magnetite.

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X-ray absorption spectroscopy measurements have been performed to elucidate local electronic and atomic structures of orthorhombic 3d-transition metal-doped yttrium manganites ͑YMnO 3 ͒ with chemical formulae YMn 2/3 Me 1/3 O 3 ͑Me= Co, Ni, and Cu͒. The Mn L 3 -and K-edges x-ray absorption near-edge structure ͑XANES͒ demonstrate the direct substitution of Me 2+ for Mn 3+ , so that the positive effective charge of Mn ions are increased. Me-doping is also found to induce substantial broadening of the Mn L 3 -edge feature, which suggests enhancement of the delocalization of Mn 3d e g subbands and conductivity. Local spin density approximation ͑LSDA͒ +U ͑Hubbard U parameter͒ calculations were used to understand their electronic structures.

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