Journal of Alloys and Compounds 486 (2009) 660–665 Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jallcom Synthesis, characterization and influence of calcination temperature on magnetic properties of nanocrystalline spinel Co-ferrite prepared by polymeric precursor method Mehrnaz Gharagozlou ∗ Department of Nanotechnology and Nanomaterials, Institute for Colorants, Paint and Coatings, P.O. Box 16765-654 Tehran, Iran article info Article history: Received 27 April 2009 Received in revised form 5 July 2009 Accepted 6 July 2009 Available online 30 July 2009 Keywords: Nanocrystalline Co-ferrite Magnetic properties Polymeric precursor method Calcination temperature abstract Magnetic particles of nanocrystalline cobalt ferrite has been synthesized successfully by polymeric pre- cursor method and the influence of the calcination temperature on the particle sizes and magnetic properties of the synthesized samples have been also investigated. The particles have been calcined at different temperatures varying from 400 to 800 ◦ C. The studies carried out using XRD, FT-IR, SEM, TEM, STA (TG–DTG–DTA) and VSM techniques. The results indicated that the ferrite samples obtained by this method had the nanocrystalline pure single-phase spinel structure and good magnetic properties. TEM images showed almost spherical nanoparticles which are uniform in both morphology and particle size distribution with sizes varied in the range of 13–145nm with the calcination temperature. The gradual increase in the crystallite size with the calcination temperature indicates the formation of bigger parti- cles on the calcination. Magnetic properties of the products were found greatly affected by the average crystalline size of the nanoparticles. The saturation magnetization and remanent magnetization values of the samples increased as a function of the calcination temperature. Our results showed this method facilitates the magnetic tunability of the Co-ferrite nanoparticles by using the proper temperature of the thermal treatment and greatly expanding the range of applications. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Ferrite magnetic materials have been intensively studied because of the fundamental understanding as well as their applica- bility in a variety of areas such as high-density information storage, magnetic printing inks, ferrofluid technology, magnetic drug deliv- ery, magnetic refrigeration, medical diagnostics, catalysts, magnetic resonance imaging enhancement and gas sensors [1–6]. Among spinel ferrites, cobalt ferrite has attracted considerable attention in recent years due to the unique physical properties such as high Curie temperature, large magnetocrystalline anisotropy, high coer- civity, moderate saturation magnetization, large magnetostrictive coefficient, excellent chemical stability and mechanical hardness [7,8]. Additionally, this material exhibits a significant higher mag- netostriction than metallic Fe or Ni. The synthesis of nanostructured magnetic materials has become an important area of research because of their applications. Due to the unique size and shape dependent magnetic, optical and elec- tronic properties, the nanostructures can be utilized as building blocks for the next generation nanodevices. The preparation of the ∗ Tel.: +98 21 22944184; fax: +98 21 22947537. E-mail address: gharagozlou@icrc.ac.ir. material from its nanoparticles is one of the promising methods to improve the magnetic properties of Co-ferrites [9]. Decreasing the size of CoFe 2 O 4 to the nanometer level is promising for applica- tions in magneto-optic devices for reducing the noise and increase the sensitivity [10]. The physical and chemical properties of spinel nanoparticles are greatly affected by the synthesis route. For this reason, various methods have been reported in the literature for the prepara- tion of these nanoscale spinel particles such as ceramic method [11], sol–gel [12], co-precipitation [13], solvent evaporation [14], hydrothermal [15], combustion [16], microemulsion [17] and cit- rate methods [18]. Many works present the synthesis of spinel ferrites using the conventional ceramic powder preparation pro- cess [11], which involves a solid state reaction of mechanically mixed metal oxides at high temperatures. This method has some disadvantages for advanced applications, such as the formation of strongly bonded agglomerates, non-homogeneities such as unde- sirable phases, abnormal grain growth, poor reproducibility and imprecise control of the cation stoichiometry [19]. In order to improve properties of the ferrite powders, chemical methods have been investigated in last years. The polymeric precursor method was developed by Pechini [20], being a soft chemical method used to synthesize polycationic pow- ders. This method consists of the formation of a polymeric resin 0925-8388/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2009.07.025