Nanostructured NiFe 2 O 4 Soft Magnetic Ferrite
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Nanostructured NiFe 2O4 Soft Magnetic Ferrite Zongtao Zhang1, Y. D. Zhang1, T. D. Xiao1, Shihui Ge 2, Mingzhong Wu2, W. A. Hines 2, J. I. Budnick2, J. M. Gromek2, M. J. Yacaman3, and H. E. Troiani 4 1 Inframat Corporation, 74 Batterson Park Road, Farmington, CT 06032 2 Physics Department and Institute of Materials Science, University of Connecticut, Storrs, CT 06269 3 Department of Chemical Engineering, University of Texas, Austin, TX 78712 4 CNM and Texas Materials Institute, University of Texas, Austin, TX 78712 ABSTRACT: NiFe2O4 is an important high frequency soft magnetic material due to its ultra high resistivity; however, its initial permeability is rather low. Conventional magnetic ferrites are manufactured through ceramic processing. In an effort to explore innovative approaches for fabricating ferrite materials with improved performance, a study of fabricating nanostructured NiFe2O4 using wet chemical approaches has been carried out. The synthetic NiFe2O4 precursor was synthesized by a citrate reaction method followed by calcinating at various temperatures. Systematic studies concerning the crystallographic structure, the nanostructure and morphology of the particle, the phase homogeneity, the conditions for chemical reaction completion, and the magnetic properties have been carried out using x-ray diffraction, transmission electron microscopy, and magnetic measurements. The results show that by using a citrate reaction approach, pure phase and stoichiometric NiFe2O4 can be fabricated easily, and the particle size can be controlled on a nanometer scale, even at high calcination temperatures. In addition, a comparative study of the NiFe2O4 fabricated by conventional ceramic processing and this new citrate processing will be presented. INTRODUCTION The development of personal computers and electronic equipment and devices is proceeding in the direction of miniaturization and high frequency operation. With high resistivity, ferrites play a leading role in many high frequency applications such as power electronics, communications, consumer electronics, and microwave equipment. Among the various types of ferrite magnetic materials [1-3], NiFe2O4 represents one of the best ferrites for ultra high frequency applications. Since their discovery in the 1940’s, ferrites were fabricated via ceramic processing which involved a solid state reaction between the constituent metal oxides at high temperatures. Although there have been a substantial improvement in the properties of conventional ferrites, the progresses are limited and the magnetic properties of the ferrites cannot satisfy the increasing demand for high quality ferrite products. In the request for improved magnetic properties, perhaps the most important task is to develop a novel synthesis approach. Based on this consideration, an aqueous solution reaction technique was developed to synthesis nanophase NiFe2O4 particles. This report deals with the synthesis of NiFe2O4, and its structural and magnetic properties. EXPERIMENTS Low temperature synthesis approaches
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