Nanoferromagnetism Of Co₃O₄ And NiO

In this paper, there is a brief introduction of definition as well as some results of diluted magnetic semiconductors and nano-ferromagnetism, with summarization of some investigation on nano-ferromagnetism. Co3O4 and NiO nanoparticles were prepared by sol-gel methods. The crystalline structures of the samples were investigated by X-ray diffraction (XRD) and selected area electron diffraction (SAED). The morphology and microstructures of the nanoparticles were studied by scan electron microscopy (SEM) and transmission electron microscopy (TEM). The magnetic properties of samples were measured by a vibrating sample magnetometer (VSM) and room temperature ferromagnetism was observed. X-ray photoelectron spectroscopy (XPS) was employed to study the origin of such ferromagnetism. The fitted XPS results of O Is and Co 2p spectra indicate that the ferromagnetism is attributed to some Co3+ irons in B sites of Co3O4 nanoparticles changing into Co2+ irons during thermal process. Regarding NiO nanoparticles, the fitted XPS results of O 1 s suggest that the formed oxygen vacancies account for the observed ferromagnetism. Meanwhile, some samples were annealed in vacuum and the changes of saturation magnetization before and after annealing were contrasted, the purpose of which is to further prove the conclusion of the origin of nano- ferromagnetism.