Synthesis and magnetic properties of ceramic MgO porous film

Ordered porous MgO films with pore diameters in the 15-28 nm range have been prepared on porous anodic alumina substrates at 573 K in a fixed O2 pressure of 1.4 × 10−4 mbar using DC-reactive magnetron sputtering. X-ray diffraction and scanning probe microscope observations have revealed that homogeneous MgO ceramics with face-centered cubic structure are formed with a highly ordered nanopore array arranged in a close packed hexagonal pattern. The results of magnetic measurements have shown that the porous MgO ceramics possess remarkable room temperature ferromagnetism and the maximum saturation magnetization along the out-of-plane direction was as high as 78 emu/cm3. Experimental and theoretical results suggest that oxygen vacancies and the unique porous structure of the films are responsible for the high magnetization. These results provide new insights into magnetic ordering in undoped dilute ferromagnetic semiconductor oxides and may be useful in the development of MgO-based spintronics devices and novel multifunctional materials.