9500313 Majetich Metal and alloy nanocrystals prepared in a carbon arc are interesting candidates for magnetic applications in xerography, magnetic resonance imaging, ferrofluids, data storage, and magnetic inks. Preliminary results demonstrate three potential advantages over existing materials: 1) the carbon coating prevents oxidation, 2) this process may be more efficient than other methods for preparing nanoparticles in the 10-100 nm size range, and 3) alloy nanoparticles with large magnetocrystalline anisotropy show room temperature magnetic stability. The research will explore scientific questions critical to the technical applications of these nanoparticles. One thrust area includes experiments to understand the formation of the carbon coating, and to correlate reaction parameters and particle morphology. This knowledge is used to optimize the growth process and to scale up production, both of which are essential for commercialization. The second thrust area focus as on magnetic characterization. Theoretical models of fine particle magnets are used to design nanoparticles with room temperature hysteresis required for data storage. After generation in the carbon are, the magnetic behavior of the nanoparticles are studied with DC and AC magnetometry, thermomagnetic analysis, Mossbauer spectroscopy, zero field NMR, and magnetic circular dichroism. The results are compared with technical benchmarks for the different applications to determine which possibilities are promising. New experimental data for alloy nanocrystals are compared with fine particle magnetism predictions to expand the fundamental understanding of hysteresis and switching rates in monodomain magnets.
