Singly-charged oxygen vacancy-induced ferromagnetism in mechanically milled SnO2 powders

The possibility of inducing long-range ferromagnetic order with non-transition metal ions has become a very exciting challenge in recent years. In order to elucidate the room temperature ferromagnetism of SnO2 powders, the magnetic properties of SnO2 powders that have been mechanically milled and subsequently annealed have been investigated. The results indicate that saturation magnetization of the samples increases with milling time, where a high saturation magnetization of 0.0012 emu g(-1) can be obtained for the sample milled for 20 h, and saturation magnetization for the sample decreases gradually after annealing in air. Electron spin resonance results show large numbers of singly-charged oxygen vacancies on the surfaces of the SnO2 powders. Combined with X-ray photoelectron spectroscopy and room temperature photoluminescence results, this suggests that the observed ferromagnetism is related to the singly-charged oxygen vacancies.