Nanostructured Magnetic Network

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9615026 Barnard A simple method has been developed for fabrication of novel nanostructured magnetic 'networks' which exhibit unique and useful magnetic properties. The networks are highly unusual in that their dimensionality can be controlled continuously at the nanometer scale allowing for exploration of confined geometries ranging from zero dimensional 'dots' to one dimensional porous networks to two dimensional films (as well as topologies with intermediate dimensions) depending on substrate nanostructure and network thickness. In preliminary studies on iron networks, dramatic enhancements in coercivity have been observed (two orders of magnitude higher than the equivalent thin film value) which are a direct result of the confinement of the iron to a network topology with critical dimensions in the range of tens of nanometers. In this research program the role of both the network material and the nanostructure of the substrate will be assessed. Comparative studies of ferromagnets with differing saturation magnetizations will be carried out to determine whether the strong shape anisotropy of the network is the primary mechanism of coercivity enhancement. The effect of the topology of the nanostructured substrate on magnetic properties of the deposited network will be studied using porous substrates with smaller pore diameters and more variable porosity than is available commercially. This part of the work will be carried out by anodically oxidizing single crystal silicon wafers. Electrochemical process parameters will be used to independently control pore diameter and arrangement as well as porosity. Magnetic characterization aimed at understanding the magnetization (and magnetization reversal) process along with the magnetic domain structure will be carried out using temperature and time dependent hysteresis studies and magnetic force microscopy. Precise dimensions of the networks and their crystallography be determined by transmission electron mic roscopy. %%% The simple fabrication of very thin, magnetically 'hard' materials is important in the context of the development of the next generation recording media. The unique network topology under study has important technological implications. For example, a particularly difficult challenge is the striction problem encountered when flying a recording head very close to the storage media. Conventional thin film media are typically roughened by mechanical or chemical means to minimize this problem. The unique surface topography of the networks should give rise to low values of stiction without further processing which will enable lower flying heights and higher recording densities. ***