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The Master of Physics Degree defense for Narayan Poudyal  was held on August 5, 2005. The title for the Master's thesis is "Synthesis and Characterization of Magnetic Nanoparticles". The abstract is given as below:

Synthesis of uniform nanoparticles (<100 nm) of hard and soft magnetic materials have attracted much attention in 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 study, synthesis and characterization of hard (FePt) and soft (Fe3O4 and CoFe2O4) magnetic nanoparticles with different size is reported. Monodisperse FePt, Fe3O4 and CoFe2O4 nanoparticles were synthesized by chemical solution methods. Particle diameter was tuned from 3 to 20 nm by varying reaction conditions or by seed-mediated growth method. Monodisperse face-centered tetragonal (fct) FePt nanoparticles in NaCl matrix to convert the fcc particles into ordered  fct structure. Morphological, structural , and compositional characterization of the nanoparticles were performed by Transimission Electron Microscope (TEM), High resolution TEM (HRTEM). Laser Particles-Size Analyzer, X-ray Diffractometer (XRD), Energy Dispersive X-ray (EDX), and Inductively Coupled Plasma (ICP). Magnetic properties of nanoparticles of different sizes at different temperatures were studied by Anternating Gradient Magnetometer (AGM), Superconducting Quantum Interference Device (SQUID), and Mssbauer Spectroscope. It has been found that all the as-synthesized Fe3O4 nanoparticles up to 20 nm were found to be superparamagnetic at room temperature while CoFe2O4 nanoparticles larger than 12 nm were 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 hard and soft magnetic nanoparticles at different temperatures have been found.

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