Charge ordering in the metal-insulator transition of V-doped CrO2 in the rutile structure

Electronic, magnetic, and structural properties of pure and V-doped CrO2 were extensively investigated utilizing density functional theory. Usually, pure CrO2 is a half-metallic ferromagnet with conductive spin majority species and insulating spin minority species. This system remains in its half-metallic ferromagnetic phase even at 50% V-substitution for Cr within the crystal. The V-substituted compound Cr0.5V0.5O2 encounters metal-insulator transition upon the application of on-site Coulomb repulsion U = 7 eV preserving its ferromagnetism in the insulating phase. It is revealed in this study that Cr3+-V5+ charge ordering accompanied by the transfer of the single V-3d electron to the Cr-3dt(2g) orbitals triggers metal-insulator transition in Cr0.5V0.5O2. The ferromagnetism of Cr0.5V0.5O2 in the insulating phase arises predominantly due to strong Hund's coupling between the occupied electrons in the Cr-t(2g) states. Besides this, the ferromagnetic Curie temperature (T-c) decreases significantly due to V-substitution. Interestingly, a structural distortion is observed due to tilting of CrO6 or VO6 octahedra across the metal-insulator transition of Cr0.5V0.5O2.