title: Effect of Nitrogen Substitution in V2O3on the Metal-Insulator Transition.
abstract: The effect of N-doping on the paramagnetic-antiferromagnetic transition associated with the metal-insulator (M-I) transition of V2O3at 150 K has been studied in bulk samples as well as in nanosheets. The magnetic transition temperature of V2O3is lowered to ∼120 K in the N-doped samples. Electrical resistivity data also indicate a similar lowering of the M-I transition temperature. First-principles DFT calculations reveal that anionic (N) substitution and the accompanying oxygen vacancies reduce the energy of the high-temperature metallic corundum phase relative to the monoclinic one leading to the observed reduction in Nèel temperature. In the electronic structure of N-substituted V2O3, a sub-band of 2p states of trivalent anion (N) associated with its strong bond with the vanadium cation appears at the top of the band of O(2p) states, the 3d-states of V being slightly higher in energy. Its band gap is thus due to crystal field splitting of the degenerate d-orbitals of vanadium and superexchange interaction, which reduces notably (ΔEg=-0.4 eV) due to their hybridization with the 2p states of nitrogen. A weak magnetic moment arises in the monoclinic phase of N-substituted V2O3with O-vacancies, with a moment of -1 μB/N localized on vanadium atoms in the vicinity of oxygen vacancies.
authors.affiliation: Chemistry and Physics of Materials Unit, International Centre for Materials Science and Sheikh Saqr Laboratory, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064 (India).
authors.forename: Nitesh
authors.initials: N
authors.lastname: Kumar
authors.affiliation: Chemistry and Physics of Materials Unit, International Centre for Materials Science and Sheikh Saqr Laboratory, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064 (India).
authors.forename: M B
authors.initials: MB
authors.lastname: Sreedhara
authors.affiliation: Theoretical Sciences Unit, Sheikh Saqr Laboratory, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064 (India).
authors.forename: Summayya
authors.initials: S
authors.lastname: Kouser
authors.affiliation: Theoretical Sciences Unit, Sheikh Saqr Laboratory, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064 (India).
authors.forename: Umesh V
authors.initials: UV
authors.lastname: Waghmare
authors.affiliation: Chemistry and Physics of Materials Unit, International Centre for Materials Science and Sheikh Saqr Laboratory, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064 (India).
authors.forename: C N R
authors.initials: CNR
authors.lastname: Rao
keywords: anion substitution; density functional calculations; magnetic properties; metal-insulator transition; vanadium oxide