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Effect of Nitrogen Substitution in V 2 O 3 on the Metal–Insulator Transition
Author(s) -
Kumar Nitesh,
Sreedhara M. B.,
Kouser Summayya,
Waghmare Umesh V.,
Rao C. N. R.
Publication year - 2015
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201500439
Subject(s) - superexchange , antiferromagnetism , chemistry , vanadium , monoclinic crystal system , band gap , magnetic moment , crystallography , paramagnetism , materials science , condensed matter physics , crystal structure , inorganic chemistry , physics
The effect of N‐doping on the paramagnetic–antiferromagnetic transition associated with the metal–insulator (M–I) transition of V 2 O 3 at 150 K has been studied in bulk samples as well as in nanosheets. The magnetic transition temperature of V 2 O 3 is 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 V 2 O 3 , 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 (Δ E g =−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 V 2 O 3 with O‐vacancies, with a moment of −1 μ B /N localized on vanadium atoms in the vicinity of oxygen vacancies.