Anomalous Hall effect governed by electron doping in a room-temperature transparent ferromagnetic semiconductor

Ferromagnetic semiconductors are believed to be suitable for future spintronics, because both charge and spin degrees of freedom(1,2) can be manipulated by external stimuli. One of the most important characteristics of ferromagnetic semiconductors is the anomalous Hall effect. This is because the ferromagnetically spin-polarized carrier can be probed and controlled electrically, leading to direct application for electronics. Control of the Curie temperature(3) and magnetization direction(4) by electronic field, and photo-induced ferromagnetism(5) have been performed successfully using the anomalous Hall effect for group III-V ferromagnetic semiconductors. In these cases, the operation temperature was much below room temperature because of the limited Curie temperature of less than 160 K (ref. 6). Here, we report on the anomalous Hall effect governed by electron doping in a room-temperature transparent ferromagnetic semiconductor, rutile Ti1-xCoxO2-delta(of oxygen deficiency delta). This result manifests the intrinsic nature of ferromagnetism in this compound, and represents the possible realization of transparent semiconductor spintronics devices operable at room temperature.