Orbital reconstruction and electrical transport behaviors of Ti-doped MgV₂O₄

Polycrystalline MgV_2-xTi_xO₄powders 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 t_2gelectrons from Ti³⁺are transferred to the t_2gorbitals of V³⁺through the 2p orbitals of oxygen, which suppress the original complex orbital order of (d_yz±d_zx)/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 temperatureT₀decreases, indicating that electron localization weakens. In the high-temperature region, the fully occupied t_2gorbitals of V²⁺can be excited more easily, leading to a reduction in the electrical activation energy ΔE. When the doping concentrationx> 1.0, excessive Ti induces Ti-Ti dimerization and forms a new orbital order with alternating occupation ofd_yzandd_zxorbitals, where electrons become confined within the Ti-Ti dimer sites. Correspondingly, the Mott temperatureT₀increases at low temperatures, while the V²⁺concentration decreases, which finally results in an increase in the activation energy ΔEat high temperatures.