Magnetic and dielectric properties study of cobalt ferrite nanoparticles synthesized by co-precipitation method
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Magnetic and dielectric properties study of cobalt ferrite nanoparticles synthesized by co-precipitation method M. Krishna Surendra, D. Kannan and M. S. Ramachandra Rao* Department of Physics, Nano Functional Materials Technology Centre and Materials Science Research Centre, Indian Institute of Technology Madras, Chennai – 600036, INDIA. * Corresponding author: [email protected] Abstract: Cobalt ferrite nanoparticles were prepared by co-precipitation method and were heat treated at 100 oC, 200 oC, 400 oC and 600 oC for 2 h to increase the particle size. Phase purity of samples was confirmed by X-ray diffraction. Scherrer formula calculations showed crystallite size varied from 12 to 24 nm when heated from 100 oC to 600 oC. Transmission electron microscopy reveals a uniform and narrow particle size distribution about 12 nm for as-prepared cobalt ferrite particles. Room temperature saturation magnetization was found to vary from 40.8 to 67.0 emu/g as the particle size increased from12 nm to 24 nm. Increase in saturation magnetization with increase in particle size was attributed to the presence of magnetic inert layer on the surface of nanoparticles. Inert layer thickness calculated at 10 K and 300 K was 6 Å and 11 Å respectively. The dielectric properties ε', tanδ, Z and θ have been studied as a function of frequency and particles size. For the 12 nm grain size, the dielectric constant is one order higher than that of bulk cobalt ferrite. Increase in the grain size showed an increase in the dielectric constant. The increase in the conductivity with grain size is mainly due to the grain size effects. The present study shows that the dielectric properties can be tailor-made to suit the requirement of a particular application by controlling the grain size. Introduction: Synthesis and assembly of magnetic nanoparticles have attracted great attention because of their potential applications in ultrahigh-density magnetic recording [1], ferrofluids [2], magnetic resonance imaging (MRI) [3], cell and DNA separation [4, 5], magnetically guided drug delivery [6], tumor hyperthermia [7], etc. Spinel ferrites have high electrical resistivity and low eddy current and dielectric losses. Cobalt ferrite is one of the potential candidates for magnetic and magneto-optical recording media [8-11]. Dielectric behavior is one of the most significant properties of ferrites which clearly depend on the preparation conditions, sintering temperature, composition and the grain size [12-14]. Dielectric studies provide important information on the behavior of localized electric charge carriers, which give rise to a better understanding of the mechanism of dielectric polarization. Fine powders of nano-sized inverse spinel type cobalt ferrite particles were synthesized using co-precipitation method. This particular method reduced the duration of preparation by avoiding sintering for long periods. Synthesis: Monodispersed CoFe2O4 nanoparticles were synthesized by co-precipitation method with cobaltous chloride (CoCl2) and ferric chloride (FeCl3) as t
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