Itinerant-electron ferromagnetism in a titanium-rich magnesium titanate ilmenite solid solution

Magnetization hysteresis loops and magnetic susceptibility were measured from Mg_0.9Ti_1.1O₃ and Mg_0.88Ti _1.12O₃ samples. The hysteresis loops revealed that the ferromagnetic transition occurs at or below 260 K. The magnetization did not reach saturation up to 70 kOe at 5 K. In contrast, stoichiometric MgTiO ₃, consisting of closed-shell ions, does not exhibit magnetic ordering. Combined magnetic susceptibility measurements, X-ray diffraction, X-ray photoelectron spectroscopy, and spin-polarized density-functional theory computations show that the ferromagnetism is due to the conduction electrons, which are responsible for the semimetallic nature of the titanium-rich magnesium titanate Mg_1-xTi_1+xO₃ solid solution. Excess Ti at the Mg-O cation layer results in a partially occupied band at the conduction band edge. This in turn shows that the magnetic properties can be controlled by a transition metal element substitution in a cation layer, which is a technological advantage.