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|Nanocrystalline ferrites and their hybrid composites|
|Nanocrystalline ferrites have interesting combination of properties such as low saturation magnetization and high electrical resistance, and crystal size of the size of a domain. These characteristics are very attractive for magneto-optical devices, and as magnetic or ferrofluids. Till recently, they have been processed by chemical and physical methods that suffer from lack of control over the crystallite size distribution. Micro-emulsion technique based on reverse micelle concept has been developed to synthesize nanocrystalline ferrites with a narrow distribution of crystallite size in the range of 5-10 nm. This route is relatively inexpensive, easy to conduct, and offers great potential to control the nature of the desired final product, promising the possibility of future developments.
The research is focused on seeking answers to the anomalous behavior of nanocrystalline ferrites, i.e., low saturation magnetization compared to the multi-domain bulk ferrite, irreversible magnetization at high fields, and non-equilibrium nature of surface spins that are canted. The high z-resolution potential of atomic force microscopy (AFM) is combined with magnetic measurements made by Superconducting Quantum Interference Device (SQUID) to examine primary issues such as surface roughness and aspect ratio on anisotropy. Attempts are being made to develop numerical models to calculate spin disorder distribution and magnetic moment that have implications for possible macroscopic tunneling in nanocrystalline ferrites. Another aspect concerns synthesis of magnetic polymer nanocomposites by mechanical milling and in situ polymerization.
Document last revised Wednesday, February 16, 2005 6:15 PM
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