Microstructures and room temperature ferromagnetism of ordered porous ZrO2 thin films sputter deposited onto porous anodic alumina substrates

Ordered porous ZrO2 films with pore diameters in the 5-45 nm range have been prepared on porous anodic alumina substrates using DC-reactive magnetron sputtering of pure Zr targets. A saturation magnetization (MS) value as high as 119 emu/cm(3) was obtained for the ZrO2 film with pores of 45 nm in diameter when the external field was perpendicular to the film surface. The significant out-of-plane saturation magnetization is associated with the porous structure of the film. Experimental and theoretical results showed that the origin of the room temperature ferromagnetism (RTFM) is closely related to the ordered porous structure and the single charged oxygen vacancies of the films. These findings suggest that porous ZrO2 films are promising to be applied to the spin electronic devices.