Abstract:
The vanadium oxide VO2 is a non magnetic metal in the high temperature rutile structure with tetragonal I42/mnm symmetry. Using first principles electronic calculations implemented in the density functional theory it has revealed that, in the LDA calculations the three t2g states are observed degenerate due to partial electron filling and orbital fluctuations between them is observed which is governed by the electron correlations. Due to these orbital fluctuations between the t2g states no band gap opens at the Fermi level. Upon the application of Coulomb repulsion of U = 4 eV, the system encounters metal to half-metal transition without any structural transitions showing ferromagnetic behaviour. In the spin up channel, dyz and dxz states remain degenerate while dx2– y2 state is more occupied than the other two and are strongly hybridized with O-2p states resulting ferromagnetism whereas in the spin down channel the Fermi level is suppressed below the V-t2g bands and V-4s states are shifted above the Fermi level causing opening of a spin gap at the Fermi level.
Keywords: Metal insulator transition (MIT), Half-metal, Coulomb repulsion, Crystal structure of VO2.
Sarajit Biswas