Composition and magnetic properties of cobalt ferrite nano-particles prepared by the co-precipitation method

• Published in: Journal of magnetism and magnetic materials 2010-11, Vol.322 (21), p.3470-3475
• Main Authors: Zhang, Yue, Yang, Zhi, Yin, Di, Liu, Yong, Fei, ChunLong, Xiong, Rui, Shi, Jing, Yan, GaoLin
• Format: Article
• Language: English
• Subjects: Annealing; Chemical synthesis methods; Co-precipitation; Cobalt ferrite nano-particles; Cobalt ferrites; Coercive force; Coercivity; Composition; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Magnetic properties; Magnetic properties and materials; Magnetic properties of nanostructures; Materials science; Methods of nanofabrication; Nanocomposites; Nanocrystals; Nanomaterials; Nanopowders; Nanoscale materials and structures: fabrication and characterization; Nanostructure; Physics
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2010.06.047

Cobalt ferrite nano-particles were prepared using the co-precipitation method followed by annealing treatment. The formation of nano-particles with different composition, microstructure and sizes were confirmed by X-ray diffraction, Raman, thermogravimetric-differential thermal analysis and transmission electron microscope. The magnetic hysteresis loops measured at room temperature revealed smaller effective magnetic anisotropy constant, coercivity and remanence ratio for the samples prepared by adding the NaOH solutions into the mixed solutions of Co 2+ and Fe 3+ ions due to the formation of Co 3+ ions. A small saturation magnetization and an enhanced coercivity were observed for the nano-particles prepared by adding the mixed solutions of Co 2+ and Fe 3+ ions into the NaOH solutions, which was related to the formation of outer layers with poor crystallization on the surfaces of the cobalt ferrite nano-crystals. Furthermore, the existence of these outer layers induced the oxidation of Co 2+ ions in cobalt ferrite nano-crystals at 200 and 300 °C, and led to a large change on the composition and magnetic properties.