Control of ferromagnetism at room temperature in (Ti,Co)O2−δ via chemical doping of electron carriers

Ferromagnetism at room temperature in (Ti,Co)O2 − δ was controlled by changing its electron density via chemical doping, where the oxygen vacancy δ served as an electron donor. With increasing the electron density, the ferromagnetic anomalous Hall effect and magnetization emerged from a paramagnetic state, while undergoing an insulator to metal transition. This result supports that the electron carriers mediated the ferromagnetic exchange interaction and is consistent with the electric field effect study on the ferromagnetism recently reported [Y. Yamada, K. Ueno, T. Fukumura, H. T. Yuan, H. Shimotani, Y. Iwasa, L. Gu, S. Tsukimoto, Y. Ikuhara, and M. Kawasaki, Science 332, 1065 (2011)].