Hindawi Publishing Corporation Journal of Nanomaterials Volume 2010, Article ID 907686, 8 pages doi:10.1155/2010/907686 Research Article Simple Synthesis and Characterization of Cobalt Ferrite Nanoparticles by a Thermal Treatment Method Mahmoud Goodarz Naseri, 1, 2 Elias B. Saion, 1 Hossein Abbastabar Ahangar, 3 Abdul Halim Shaari, 1 and Mansor Hashim 1, 4 1 Department of Physics, Putra University, Malaysia (UPM), 43400 Serdang, Selangor, Malaysia 2 Department of Physics, Faculty of Science, Malayer University, Malayer, Iran 3 Department of Chemistry, Putra University, Malaysia (UPM), 43400 Serdang, Selangor, Malaysia 4 Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology, Putra University, Malaysia (UPM), 43400 Serdang, Selangor, Malaysia Correspondence should be addressed to Mahmoud Goodarz Naseri, mahmoud.naseri55@gmail.com Received 4 July 2010; Revised 20 November 2010; Accepted 26 November 2010 Academic Editor: Michael Harris Copyright © 2010 Mahmoud Goodarz Naseri et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Crystalline, magnetic, cobalt ferrite nanoparticles were synthesized from an aqueous solution containing metal nitrates and polyvinyl pyrrolidone (PVP) as a capping agent by a thermal treatment followed by calcination at various temperatures from 673 to 923 K. The structural characteristics of the calcined samples were determined by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM). A completed crystallization occurred at 823 and 923 K, as shown by the absence of organic absorption bands in the FT-IR spectrum. Magnetization measurements were obtained at room temperature by using a vibrating sample magnetometer (VSM), which showed that the calcined samples exhibited typical magnetic behaviors. 1. Introduction The spinel ferrite structure with the formula of MFe 2 O 4 (M = Co, Ni, Zn, or other metals) can be described as a cubic, closely packed arrangement of oxygen atoms, and M 2+ and Fe 3+ ions can occupy either tetrahedral (A) or octahedral (B) sites [1]. Spinel ferrite nanoparticles have attracted much attention because of their electronic, magnetic, and catalytic properties, all of which are different from those of their bulk counterparts. Among spinel ferrites, cobalt ferrite (CoFe 2 O 4 ) has an inverse spinel structure in which, in the ideal state, all Co 2+ ions are in B sites, and Fe 3+ ions are equally distributed between A and B sites. Cobalt ferrite has been widely studied due to its high electromagnetic performance, excellent chemical stability, mechanical hardness, high coer- civity, and moderate saturation magnetization, which make it a good candidate for the electronic components used in computers, recording devices, and magnetic cards [2–4]. These properties are dependent on chemical composition and microstructural characteristics, which can be controlled in the fabrication and synthesis processes. In order to acquire materials with the desired phys- ical and chemical properties, the preparation of cobalt ferrite nanoparticles through different routes has become an important area of research and development. Various methods of synthesizing spinel cobalt ferrite nanoparticles have been reported, such as ball milling [5], a ceramic method by firing [5], coprecipitation [5–7], reverse micelles [8], hydrothermal methods [9, 10], a polymeric precursor [11], sol-gel [12], microemulsions [13], laser ablation [14], a polyol method [15], sonochemical approaches [16], and aerosol method [17]. Various precipitation agents have been used to prepare cobalt ferrite nanoparticles of a specific size and shape, for example, metal hydroxide in the co- precipitation method, surfactant and ammonia in the reverse micelles and microemulsion methods, and organic matrices