Recent advances of ferromagnetism in traditional antiferromagnetic transition metal oxides

Transition metal oxides (TMOs) play an important role in scientific research and technological advance. Attributing to the excellent physical and chemical properties, they have been widely used in semiconductors, sensors, photoelectric devices, catalysis and many other fields. However, majority of the TMOs are nonmagnetic or antiferromagnetic, so the lack of intrinsic ferromagnetism hinders their applications in spintronics. In the meantime, as the study continues, it has become indispensable to have a thorough understanding about the mechanism of magnetism from the perspective of electronic states and explore a variety of new magnetic materials to meet the growing demands. In such a context, if the room-temperature ferromagnetism could be introduced into TMOs, especially for traditional antiferromagnetic TMOs, they will be ideal candidates for the future spintronics devices, and certainly push the theoretical investigation and experimental exploration move forward. In this review, we retrospect the recent studies that focus on ferromagnetic properties of antiferromagnetic TMOs, highlight several representative methods that being used to induce intrinsic ferromagnetism in TMOs, such as elements doping, defect-construction and ions or proton-implanting. Herein, the feasibility of aforementioned induction methods is demonstrated via experimental approaches, and the mechanism how to generate net magnetic moments and then establish long-range magnetic ordering is illustrated by means of theoretical calculations. Finally, we probe other experimental factors that may affect the ferromagnetism and infer some promising strategies that deserve to be investigated deeply, aiming to have a outlook on the development of spintronics.