Room temperature ferromagnetism in D-D neutron irradiated rutile TiO2 single crystals

Room temperature ferromagnetism (RTFM) was observed in unirradiated rutile TiO2 single crystals prepared by the floating zone method due to oxygen vacancy (V-O) defects. D-D neutrons mainly collide elastically with TiO2, producing V-O, titanium vacancies (V-Ti) and other point defects; the density and kind of defect is related to the neutron irradiation fluence. D-D neutron irradiation is used to regulate the concentration and type of defect, avoiding impurity elements. As the irradiation fluence increases, the saturation magnetization (M-s) first increases, then decreases and then increases. To verify the origin of RTFM, the CASTEP module was used to calculate the magnetic and structural properties of point defects in TiO2. V-O induces a 2.39 mu(B) magnetic moment, Ti3+ and F+ induce 1.28 mu(B) and 1.70 mu(B) magnetic moments, respectively, while V-Ti induces a magnetic moment of similar to 4 mu(B). Combining experimental and theoretical results, increases in V-O concentration lead to M-s increases; more V-O combine with electrons to form F+, inducing a smaller magnetic moment. V-O and V-Ti play a key role and M-s changes accordingly with larger fluence. V-O, F+ and V-Ti are the most likely origins of RTFM.