Room-temperature ferromagnetism has been observed in Porous Anodic Aluminum (PAA) tliin films, with an out-of-plane saturation magnetization of 60 emu cm~(-3). The significant out-of-plane saturation magnetization is associated with the porous structure of the film. As there were no magnetic impurities present, the origin of the ferromagnetism is most likely due to exchange interactions between localized electron spin moments resulting from oxygen vacancies in the films. A similar hysteretic behavior is observed in porous thin films of nonmagnetic TiO2 and ZnO. This suggests that ferromagnetism may be a universal characteristic of porous thin films of nonmagnetic metal oxides. Our present results suggest a promising direction for research in spintronic devices.
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