Linear dichroic x-ray absorption response of Ti-Ti dimers along the c axis in Ti2O3 upon Mg substitution

Corundum oxide Ti2O3 shows the metal-insulator transition around 400-600 K accompanying the nearest Ti3+-Ti3+ bond (a1ga1g singlet state) formation along the c axis. In order to clarify the hole-doping effect for the a1ga1g singlet bond in Ti2O3, we investigated Ti 3d orbital anisotropy between corundum-type Ti2O3 and ilmenite-type MgTiO3 using linear dichroism of soft x-ray absorption spectroscopy of the Ti L2,3 edge. From the linear dichroic spectral weight in MgyTi2-yO3, we confirmed that the a1ga1g state is dominant not only in y = 0.01 (almost Ti2O3), but also in y = 0.29, indicating that the Ti-Ti bond survives against a certain level of hole doping. In y = 0.63 corresponding to 46% hole doping per Ti, the 3d orbital symmetry changes from a1g to e pi g.

Automated summary

The research investigates the differences in the titanium 3d orbitals between corundum-type Ti2O3 and ilmenite-type MgTiO3 using linear dichroism of soft x-ray absorption spectroscopy. The study confirms the presence of the Ti-Ti bond and the change in symmetry of the 3d orbitals under hole doping.