Nanostructured Magnetic Networks

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9713497 Barnard This is a systematic study of processing/microstructure/magnetic property interrelationships in nanostructured magnetic networks. The project objectives include fabrication of a set of networks of varying dimensions and magnetic materials, quantitative assessment of network microstructure and topology, determination of the physical origin of the unusual magnetic properties, and evaluation of the potential of network materials as magnetic recording media. Networks are fabricated using simple sputter deposition onto the surface of nanostructured substrates (nanochannel alumina), e-beam lithography, and naturally phase separating systems. Quantitative microstructural and topological characterization are carried out in both the as-deposited and annealed states using a combination of scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The nanostructural characteristics (crystallite size, crystallographic texture, etc.) of the networks are documented by transmission electron microscopy and selected area electron diffraction. Magnetic characterization and correlation of magnetic properties with network geometry and dimensions are at the core of this proposal. A multitechnique approach including temperature dependent measurements, annealing studies, magnetic imaging, and ferromagnetic resonance are used to develop an understanding of network magnetic domain structures, reversal mechanisms, and stability. The unique topology of the networks proposed here allows for detailed study of the effects of transitioning from traditional continuous film media (nanoscale in one dimension, the thickness) to media comprised of discrete pillars, bars, and dots (nanoscale in two or three dimensions). This research project is particularly strong in the areas of educational and human resources development. The program is multidisciplinary and has strong fundamental and technological components. Both the graduate stude nt and post-doc budgeted for the project employ aspects of solid state physics, metallurgy, thin film science, magnetic characterization, materials processing, microstructural characterization, and materials selection. %%% Nanostructured networks are a unique geometry which exhibit unusual and potentially useful magnetic behavior associated with their the small dimensions and novel topology. A nanostructured network is a contiguous topology which may be pictured as a thin film with a high density of holes or pores. When the pore size, mean pore separation, and network thickness approach nanoscale dimensions, strong confinement effects on magnetic properties (such as increases in coercivity of more than two orders of magnitude over continuous films of equivalent thickness) are observed. Networks are unique in that their dimensionality can be continuously controlled at the nanometer scale by varying the thickness, pore size, and porosity. The properties of magnetic networks are only beginning to be explored.