Effect of Fe Doping and O Vacancies on the Magnetic Properties of Rutile TiO2

Magnetism sources of Fe doping and O vacancies, which coexist in the presence of rutile TiO2, are controversial and require a resolution. The effects of Fe doping and point defect on the magnetism of rutile TiO2 were studied using geometry optimization and energy calculation based on the first principle generalized gradient approximation + U method (GGA+U) of density functional theory. Fe/Vo ratio is 1:1 in rutile TiO2. The next closest distance between Fe and Vo is 0.04082 nm. The formation energy of the doping system is the smallest. This doping system has the highest stability. The coexistence of Fe doping and O vacancy achieved ferromagnetic long-range order. The different ratios of Fe/Vo are 1:1, 1:2, 2:1, and 2:2. The magnetic properties of the doping system are significantly different. At a ratio of 2:1, the magnetic moment is the largest among all doping systems. Moreover, the Curie temperature of the doping system can be higher than room temperature. These findings can obtain dilute magnetic semiconductors with potential application value. At a Fe/V-O ratio of 2:2, the Ti14Fe2O30 system produces a half-metallic property of 100% electron spin polarizability. This is the most valuable application for designing and preparing novel spintronic injection source dilute magnetic semiconductors. The magnetic source is mainly mediated by the holes generated by Fe doping and O vacancy complexes, thereby causing the spin polarization double exchange effect on the electron of Ti-3d orbital atoms near the O vacancy, O-2p electron orbital, and Fe-3d electron orbital. This feature is consistent with the following theories: the mean field approximation and the double exchange mechanism theories.