We report the room temperature ferromagnetism (RTF) of pure ZnO nanoparticles, which were prepared by coprecipitation method. Magnetization measurement indicates that the ZnO nanoparticles annealed in air at 450, 550, 650, and 800 °C exhibit the RTF and the decrease in the ferromagnetism is performed with the increase in annealed temperature. Selected area electron diffraction, x-ray diffraction, and x-ray photoelectron spectroscopy measurements show that all the samples possess a typical wurtzite structure and no other impurity phases are observed. The results of the Raman spectra indicate that there are lots of defects existing in the fabricated samples. It is also found that the ferromagnetism of ZnO nanoparticles increases after annealing in vacuum condition and decreases after annealing in a rich-oxygen atmosphere. These results confirm that the oxygen vacancies play an important role in introducing ferromagnetism for the ZnO nanoparticles in our case.

Nanowire-like iron oxides (α-Fe2O3, Fe3O4 and γ-Fe2O3) of diameter about 200 nm and length up to 8 µm were assembled into anodic aluminium oxide templates through electrodeposition followed by a heat-treating process. These wires have polycrystalline structures and consist of fine particles whose magnetic moments have preferred orientations in the templates. Some unique magnetic properties, such as perpendicular magnetic anisotropy in Fe3O4 wires, reduced transition temperature in α-Fe2O3 and Fe3O4 wires, and superparamagnetism in γ-Fe2O3 wires, were observed. The properties can be understood by their unique structures induced by reduced dimension and the competition of the shape and crystalline anisotropy.

Arrays of α-Fe2O3 nanowires embedded in anodic alumina membranes were obtained after heat-treating β-FeOOH nanowire arrays fabricated by electrochemical deposition. Haematite polycrystalline nanowires with maximum length of about 7µm and average diameter of about 120 nm were characterized by means of x-ray diffraction and transmission electron microscopy. The Morin temperature below 80 K and Néel temperature of about 350 K for the α-Fe2O3 nanowire arrays, far lower than those of bulk material, were measured by Mössbauer spectroscopy and using a Magnetic Property Measurement System.

Stripe domain (SD) in obliquely sputtered permalloy films were investigated by comparing with normally sputtered ones. The critical thickness for SD formation of obliquely sputtered films was about 100 nm thinner than that of normally sputtered films. The hysteresis loops of obliquely sputtered films showed a peculiar shape. A rotation of SD towards easy axis was observed in the obliquely sputtered films, which was confirmed by permeability spectra under a bias field. The origin of the rotation could result from in-plane uniaxial anisotropy, which is induced by the shape effect of the oblique columnar growth of permalloy grains.

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