Synthesis and characterization of magnetic nanoparticles

Synthesis of uniform nanoparticles (<100 nm) of hard and soft magnetic materials have attracted much attention in the last two decades because of their unique magnetic properties and potential for many applications such as high density recording media, biotechnology, ferrofluids, and fabrication of exchange-coupled nanocomposite permanent magnets. In this thesis, synthesis and characterization of hard (FePt) and soft (Fe3O4 and CoFe2O4) magnetic nanoparticles with different sizes are reported. Monodisperse FePt, Fe3O4 and CoFe 2O4 nanoparticles were synthesized by chemical solution methods. It has been found that all the assynthesized Fe3O4 nanoparticles up to 20 nm are superparamagnetic at room temperature while CoFe2O 4 nanoparticles larger than 12 nm are ferromagnetic. An exchange bias field up to 3 kOe was observed for 3 nm CoFe2O4 nanoparticles in field cooling measurements. Very high coercivity of the isolated fct FePt nanoparticles up to 30 kOe at room temperature has been obtained. Interesting experimental results on the size dependent magnetic properties for both the hard and soft magnetic nanoparticles at different temperatures have been found. (Abstract shortened by UMI.)...