ELECTRON-ENERGY-LOSS SPECTROSCOPY STUDY OF THE METAL-INSULATOR-TRANSITION IN V2O3

Electron energy-loss spectra of V2O3 Of the paramagnetic metallic (PM) and antiferromagnetic insulating (AFI) phases have been measured by a high-resolution transmission electron energy loss spectroscopy (EELS) technique. An excitation at about 1 eV was previously observed in bot h the PM and AFI phases by an optical measurement and assigned to the excitation of a free-carrier plasmon. A sharp peak has, however, been observed at 1.1 eV in our EELS spectra of the PM phase but not in thos e of the AFI phase. We assigned the peak to an interband plasmon due t o d-d transitions by inspecting the dielectric function derived from t he EELS spectra. The peak of the O 1s EELS spectra due to the O 1s --> V 3d(t(2g)) transition increased in energy by 0.4 eV but decreased in intensity at the transition from the PM phase to the AR phase. The in crease of the energy is due to a splitting of the V 3d(t(2g)) band, wh ich is partly filled at the PM phase, into the fully occupied and unoc cupied bands and a shift of the unoccupied band to an energy higher th an the Fermi level in the PM phase. The decrease of intensity is consi dered to be due to the decrease of the transition probability of the O 1s --> V 3d(t(2g)) transition, which is attributed to the decrease of the hybridization of the V 3d with O 2p orbitals at the transition fr om the PM phase to the AFI phase.