Fabrication and Characterization of Multilayer Nanostructures of Manganites

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9707687 Li This Research Planning Grant(RPG) addresses synthesis and processing issues in the fabrication of trilayer tunnel junctions and multilayer nanostructures of manganites. Based on results of magnetoresistance effects, a large spin-polarized tunneling effect is expected in manganites because of the large degree of spin polarization in these materials. The approach is to use artificially fabricated trilayer junctions and multilayer structures as tailored systems with controlled junction parameters to systematically study the phenomena. The objective during the planning period is to study the feasibility of fabricating and characterizing small-area multilayer tunnel junctions using the National Nanofabrication Facilities at Penn State. Principal research areas to be pursued are: 1) epitaxial growth of artificial trilayer junction structures consisting of two manganite layers separated by a thin insulating barrier layer with sharp interfaces and low leakage. Different insulator layers will be tested and the structural and interfacial properties of the junction will be characterized; 2) lithographically pattern the junction into small with the goal of achieving single magnetic domain in both manganite layers with the magnetic moment in each layers antiparallel; 3) study spin-dependent magneto-transport and magnetic properties of the junctions with different junction sizes, manganite layer thicknesses, and barrier layer materials and thicknesses. It is anticipated that the feasibility of the project will be ascertained, and a systematic study on the effect of spin-polarized tunneling in manganites, their relation with sample structures and parameters, and a comparison with theoretical models will follow. %%% The project addresses basic research issues in a topical area of materials science having technological relevance to electronics. These studies are important for greater understanding of spin-polarized transport in general, and the anomalous magnetoresistance effects in manganite thin films and polycrystalline samples in particular. At the same time, the current research also addresses issues directly related to the technologies and therefore has direct impact on the potential application of the colossal magnetoresistance materials. ***