SGER: Realization of Half-Metallicity in Magnetite

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TECHNICAL: While attractive to many, true half-metals have not been observed experimentally. The room temperature value of the spin polarization falls far short of 100% for all theoretically predicted half-metals. The experimentally reported room temperature spin polarization of Fe3O4 varies between 20 and 80%. Several factors may contribute to the lack of metallicity, including surface oxidation and reconstruction, presence of magnons, surface magnetic state being different from the bulk, and the properties of the barrier materials when the experiments involve magnetic tunneling junctions. In this project, an innovative and exploratory approach to unveil the spin polarization of Fe3O4 is to be investigated. Ultra thin oxygen-free organic overlayers will be applied to the surfaces of Fe3O4 to prevent its oxidation and to lift the reconstruction with the ultimate goal of restoring the true spin polarized nature on its surfaces. Understanding that achieving 100% spin polarization may be difficult, this investigation also aims at the realization the highest possible half-metallicity in Fe3O4. Both high quality epitaxial films and cleaved surfaces of single crystal Fe3O4 will be prepared. A group of organic overlayers that show promise for the stated purposes, including styrene, thiols, graphene and carbon ?dusting?, will be deposited on the surfaces. The chemical and structural properties and spin polarization of the surfaces with/without overlayers will be investigated with state-of-the-art characterization tools and magnetic tunnel junctions will be made for additional spin polarization measurements. Due to the unavoidable presence of the surface states that are different from the bulk, it has been an extremely difficult task to probe the true spin polarization of Fe3O4. The project points to a novel and promising way to overcome such obstacle by applying overlayers on various surfaces of Fe3O4. Such efforts to protect the surfaces from oxidation and, in particular, to lift the reconstruction have not been tested before, and the risk is high in terms of the outcome of the project. However, the potential impact will be tremendous as it leads to a completely new and transformative approach to reveal the bulk spin-resolved electronic properties. NON-TECHNICAL: If successful, realizing half-metallicity in Fe3O4 will be groundbreaking to the spintronic materials research and will have a huge impact on the science and technology of spintronics. This high risk high payoff project should have a direct economic impact on the future information technology. Both graduate and undergraduate students, especially underrepresented minorities and females, will be provided with training opportunities in condensed matter physics and materials science that are strongly linked to advanced technology.