Preparation And Characterization Of Hard Magnetic Nanoparticles

Hard-magnetic nanoparticles with uniform size distribution have attracted huge attention in the past several years because of their unique magnetic properties and potential for many applications such as high density recording media, exchange-coupled nanocomposite permanent magnets and biomedical applications. In this thesis, preparation and characterization of hard magnetic nanoparticles with different sizes are reported. Monodisperse FePt nanoparticles with face-centered cubic (fcc) structure were synthesized by chemical solution method and particle diameter was tuned from 2 to 15 nm by varying reaction conditions. Monodisperse hard-magnetic FePt nanoparticles with ordered face-centered tetragonal (fct) structure were prepared by the salt-matrix annealing technique. Morphological, structural, and compositional characterizations of the nanoparticles were performed by Transmission Electron Microscopy (TEM), high resolution TEM (HRTEM), X-Ray Diffractometer (XRD), and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) analyses. Magnetic properties of nanoparticles of different sizes were studied by Alternating Gradiant Magnetometer (AGM), Superconducting Quantum Interference Device (SQUID) magnetometer and Vibrating Sample Magnetometer (VSM). It has been found that particle size has significant effect on the characteristics of the fct FePt nanoparticles, such as long-range ordering parameter, coercivity and Curie temperature.