Orbital reconstruction and electrical transport behaviors of Ti-doped MgV2O4

Polycrystalline MgV2-xTixO4 powders were synthesized by the solid-state reaction method. It is found that the resistivity does not decrease monotonically with increasing Ti concentration. During the doping process, the t2g electrons from Ti3+ are transferred to the t2g orbitals of V3+ through the 2p orbitals of oxygen, which suppress the original complex orbital order of (dyz±dzx)/√2 and thereby induces orbital reconstruction. For 0 ≤ x ≤ 1.0, as the Ti doping concentration increases, more V3+ is converted to V2+. In the low-temperature region, the Mott characteristic temperature T0 decreases, indicating that electron localization weakens. In the high-temperature region, the fully occupied t2g orbitals of V2+ can be excited more easily, leading to a reduction in the electrical activation energy ΔE. When the doping concentration x > 1.0, excessive Ti induces Ti-Ti dimerization and forms a new orbital order with alternating occupation of dyz and dzx orbitals, where electrons become confined within the Ti-Ti dimer sites. Correspondingly, the Mott temperature T₀ increases at low temperatures, while the V2+ concentration decreases, which finally results in an increase in the activation energy ΔE at high temperatures.