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 1eV was previously observed in both 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 those of the AFI phase. We assigned the peak to an interband plasmon due to d-d transitions by inspecting the dielectric function derived from the 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 AFI phase. The increase of the energy is due to a splitting of the V 3d(t_2g) band, which is partly filled at the PM phase, into the fully occupied and unoccupied bands and a shift of the unoccupied band to an energy higher than the Fermi level in the PM phase. The decrease of intensity is considered 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 from the PM phase to the AFI phase.