Mechanism Of Multi-Defect Induced Ferromagnetism In Undoped Rutile Tio2

Based on first-principles calculations, the coexistence of Ti vacancies (V-Ti) and O vacancies (V-O) is first considered to study the origin of the ferromagnetic ordering in undoped rutile TiO2. The calculations show that V-O can induce local magnetic moments in TiO2, however, the ferromagnetic (FM) exchange interaction of two V-O is not strong enough to induce room-temperature (RT) ferromagnetism on their own in undoped TiO2. The FM coupling between two V-Ti is about four times stronger than that between two V-O. More importantly, the FM coupling between two V-Ti is further enhanced after V-O is introduced. Our results indicate that the electrons induced by V-O mediate the long-range FM exchange interaction between two distant V-Ti. This maybe the ferromagnetism mechanism in undoped TiO2: V-Ti produce local moments while the electrons induced by V-O mediated the long-range FM exchange interaction. The results are in excellent agreement with the experimental evidences that V-O alone cannot induce RT ferromagnetism while V-O can promote the ferromagnetic ordering in undoped TiO2. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.