Carrier-induced metal-insulator transition in trirutile MgTa2O6

Materials exhibiting metal-insulator transitions (MITs) are proposed platforms for next-generation low-power electronics. Many of these materials exhibit strong coupling between the electronic and lattice degrees of freedom, which makes them ideal systems to examine the interplay between lattice dynamics, electronic structure, and magnetic order. The rutile structure, featuring edge-connected octahedral chains along its $c$ axis, permits metal-metal interactions that can induce metal-insulator transitions. Although the MITs in rutile-structured compounds have been thoroughly studied, the derivative trirutile phase, which accommodates similar metal-metal interactions, has yet to be examined in the context of MITs. Here we use density functional theory calculations to investigate a carrier-driven MIT in trirutile ${\mathrm{MgTa}}_{2}{\mathrm{O}}_{6}$, a ${d}^{0}$ insulator with a suitable axial ratio. Our calculations suggest the existence of four distinct phases in ${\mathrm{MgTa}}_{2}{\mathrm{O}}_{6}$ with increasing electron concentration: nonmagnetic insulator, ferromagnetic (FM) metal, FM half-metal, and nonmagnetic insulator. We explain how the resulting electronic phases arise from changes in atomic structure with increasing carrier density. Our results indicate that trirutile oxides may be a promising materials class for which to access and functionalize MITs.