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In studies of weak magnetism in diluted magnetic semiconductor thin films, there is often a significant difficulty in subtracting the background signal arising from the substrate. In the present work, an improved magnetic correction method is proposed. For Al doped ZnO and Fe doped TiO2 films, the magnetic moment and coercivity of the samples were corrected by the improved method, and the maximum fitting error due to the glass substrate was calculated. The accuracy and rationale of the improved method are discussed and compared with the traditional method. The results show that room temperature ferromagnetism is observed in Fe doped TiO2 thin films. The ferromagnetism is strongly correlated with the substitution of Ti by Fe in the TiO2 lattice, which results in a change in the crystal structure and the quality of the crystallization of the TiO2 films. The changes are responsible for altering ferromagnetism in the films.

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For this study, porous anodic alumina thin films with annular structural colors were fabricated in a phosphoric acid electrolyte by the one-step oxidation of an aluminum (Al) sheet. In this case, small carbon balls were used as the cathode and an Al sheet used as the anode, with the distance between cathode and anode remaining adjustable. Electron microscopy shows that the different parts of films are different in microstructure. Results additionally reveal that the depth and aperture of nano-holes diminished symmetrically outward from the center of the films. It is possible to control ring density by changing the oxidation time and voltage. These experimental results, conducted using point electrode, are consistent with a theoretical study of the oxidation process and formation mechanism of anodic alumina thin films with annular structural colors.