Diluted magnetic semiconductors (DMS) have recently attracted considerable attention due to their potential applications for spintronic devices. ZnCoO is one of the most promising diluted magnetic semiconductors materials due to its room temperature ferromagnetism. In this study, Al₂O₃ layer was conformally deposited on the surface of polystyrene (PS) nanoshpere with different diameter (300nm~800nm) by atomic layer deposition (ALD). After removal of PS nanosphere by heating, Al₂O₃ hollow nanospheres were formed. Then the Zn_1-xCo_xO ( x=0.03, 0.05, 0.07) coatings were grown on Al₂O₃ hollow nanospheres by pulsed laser deposition(PLD). According to the results of high-resolution x-ray diffraction, Co-doping does not change the wurtzite structure of ZnO and the Zn_1-xCo_xO hollow nanospheres are polycrystalline. The surface and cross-section morphologies of the hollow nanospheres were analyzed using a field-emission scanning electron microscope (FE-SEM). Photoluminescence spectra demonstrate ultraviolet emission peaks which have shift with the increase of Co ion concentration. The magneto-optical properties of the nanospheres were measured by micro-MOKE and x-ray magnetic circular dichroism (XMCD) spectroscopy. The results show the magnetic properties of Zn_1-xCo_xO hollow nanospheres strongly depend on the Co composition fraction.

In this paper, the electronic, magnetic and structural properties of (Fe₂O₃)_n (n = 2-5) clusters were studied using Density Functional Theory. It came out that the most stable structures for n = 2, 3 and n = 4, 5 were ferrimagnetic and antiferromagnetic, respectively. The states with completely geometrical symmetry were spin-symmetric also, i.e. had equal atomic magnetic moments. It was found that by increasing ‘n’, the binding energy (E_b) increased, while such an observation was not seen for n = 4 and n = 5 and the binding energies were equal in these cases. An interesting result was that one of the states for n = 4 (n4-1) was a half-metallic antiferromagnet, which is important in spintronics applications. The most of the considered clusters were semi-metal or half-metal due to presence of Fe atoms.