The effect of Cr-substitution on the structural, electronic and magnetic properties of rutile VO2

The effect of Cr-substitution on the structural, electronic and magnetic properties of rutile VO ₂ is investigated in this study. Pure VO ₂ is found to be a nonmagnetic metal, whereas all three Cr- substituted compounds [V _1-xCr _xO ₂ (VCO) with x = 0.25, 0.5, 0.75] are found to exhibit ferrimagnetic metallic behaviour. However, pure and all VCO compounds encounter metal to half-metal transition for the application of U = 2 eV, showing ferromagnetism. VO ₂, the VCO compounds V _0.75Cr _0.25O ₂ and V _0.5Cr _0.5O ₂ undergo metal–insulator transition (MIT) for U = 5 eV, 5.5 eV and 3.5 eV respectively, preserving ferromagnetism. Besides, V _0.25Cr _0.75O ₂ preserves its ferromagnetic half-metallic character even application of U as high as 6 eV. The breaking of mirror symmetries in the VO ₆/CrO ₆ octahedra induces structural distortions in all three VCO compounds. The MIT in pure VO ₂ is caused by the transfer of electrons from the V-d _yz and d _xz states to the d _x ² _{- y} ² states. The simultaneous effect of structural distortion, V ⁴⁺- V ⁴⁺ and Cr ³⁺-V ⁵⁺ charge ordering and U is responsible for the MIT in V _0.75Cr _0.25O ₂. On the other hand, the simulteneous effect of structural distortion, transfer of electrons from V-t _2g to Cr-t _2g states and U is responsible for the MIT in V _0.5Cr _0.5O ₂. Although electron transfer is commenced from V-t _2g to Cr-t _2g states in V _0.25Cr _0.75O ₂, the latter cannot be completely occupied by the transferred electrons, resulting in the non-opening of a band gap near the Fermi level. The p-d hybridization between O-2p and V-3d/Cr-3d states, and V/Cr-O antiferromagnetic coupling facilitates ferromagnetism in insulating VO ₂, V _0.75Cr _0.25O ₂, V _0.5Cr _0.5O ₂ and half-metallic V _0.25Cr _0.75O ₂.