Theoretical analysis of electronic and magnetic properties of NaV2O4: Crucial role of the orbital degrees of freedom

Abstract

Using a realistic low-energy model with parameters derived from the first-principles electronic structure calculation, we address the origin of the quasi-one-dimensional behavior in orthorhombic NaV 2O 4, consisting of the double chains of edge-sharing VO 6 octahedra. We argue that the geometrical aspect alone does not explain the experimentally observed anisotropy of electronic and magnetic properties of NaV 2O 4. Instead, we attribute the unique behavior of NaV 2O 4 to one particular type of the orbital ordering, which respects the orthorhombic Pnma symmetry. This orbital ordering acts to divide all t 2g states into two types: The "localized" ones, which are antisymmetric with respect to the mirror reflection y→-y, and the symmetric "delocalized" ones. Thus, NaV 2O 4 can be classified as the double exchange system. The directional orientation of symmetric orbitals, which form the metallic band, appears to be sufficient to explain both quasi-one-dimensional character of interatomic magnetic interactions and the anisotropy of electrical resistivity. © 2012 American Physical Society.