Effect of Nitrogen Substitution in V₂O₃ on the Metal–Insulator Transition

Abstract

The effect of N-doping on the paramagnetic-antiferromagnetic transition associated with the metal-insulator (M-I) transition of V O at 150 K has been studied in bulk samples as well as in nanosheets. The magnetic transition temperature of V O 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 O , 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 (ΔE =-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 O with O-vacancies, with a moment of -1 μ /N localized on vanadium atoms in the vicinity of oxygen vacancies.

Influence of Nitrogen Substitution on the Electronic Structure of Ti2O3: Insights into the Doping‐Induced Insulator‐to‐Metal Transition

“…For example, N substitution in V 2 O 3 decreases the IMT transition temperature. [ 13 ] Recently, Chouteau et al [ 14 ] have also demonstrated that N doping into VO 2 can cause the insulator monoclinic‐to‐metallic tetragonal phase transition, with a decreased T c from 68 °C to 50 °C. Important realization include chemical doping may activate or enhance the dimerization linked to the shortening of interatomic distances.…”