Orbital reconstruction and electrical transport behaviors of Ti-doped MgV2O4.

Polycrystalline MgV2-xTixO4powders 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 t2gelectrons from Ti3+are transferred to the t2gorbitals of V3+through the 2p orbitals of oxygen, which suppress the original complex orbital order of (dyz±dzx)/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 t2gorbitals 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 ofdyzanddzxorbitals, 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.