Theory on electronic structure and phase transitions in V 2O 3

Abstract

The electronic structure and phase transitions in pure and Cr-doped V 2O 3 are studied in relation to the 3d spin–orbit interaction and the monoclinic lattice distortion. AV ion cluster model consisting of the V ion pair along the corundum c-axis is studied within the many-body point of view. No orbital ordering is expected to be present in the antiferromagnetic insulating (AFI) phase and instead of this a large orbital magnetic moment ∼0.7μ B exists. In the AFI and paramagnetic insulating (PI) phases, Jahn–Teller like lattice instability causes tilting of the V ion pairs from the c-axis. To study the AFI to PI transition, exchange interaction between the V ion pairs is deduced from the second-order perturbation theory and an effective spin–lattice Hamiltonian is proposed. The transition is found to be a simultaneous order–disorder transition of the magnetic moments and the tilting of the V ion pairs.