Structure-Composition-Property Relationships in Complex Intermetallic Phases: Experimental and Theoretical Studies

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This project involves combining experimental and theoretical approaches to search for and study new complex intermetallic compounds that will have interesting structural and magnetic properties with possible applications to environmentally friendly refrigerants and magnetic sensors. The compounds targeted consist of active metals (sodium, potassium, strontium, barium, rare-earths) with combinations of magnetic elements (iron, cobalt, nickel) and the post-transition elements (aluminum, germanium, indium, and silicon): such compounds should adopt beautifully complex structures involving metal clusters that are controlled by optimizing metal-metal bonding, but also showing arrangements giving interesting magnetic properties through exchange interactions coupled to their orbital overlaps, i.e., magnetocaloric effects and magnetostriction. These studies will lead to fundamental understanding of how intermetallic compounds form and the factors that control structure in magnetic systems. If we are successful to optimize the magnetocaloric effect, we may find a material effective for refrigeration near room temperature that is environmentally benign and economically feasible. Young scientists will learn state-of-the-art techniques in air-sensitive, high temperature synthesis, diffraction and in the theoretical calculation of electronic structure, which will prepare them for numerous career opportunities in industry or academia. This project is designed to form and study new compounds between different metallic elements, called intermetallic compounds. One component of these new compounds will be magnetic elements, like iron or cobalt, which will allow us to probe new compounds to serve as materials for refrigeration in place of chlorofluorocarbons ("magnetic refrigeration"). Such compounds use magnetism to perform refrigeration, which is a more efficient process and the materials are also more environmentally friendly than current substances. An important fundamental goal of this research is to understand what factors control the formation and growth of intermetallic compounds, so that we may ultimately be able to design materials with specific electrical or magnetic properties. We plan to achieve this goal by searching for new intermetallic compounds through careful synthesis, through measurement of the structure and arrangement of elements in their crystals, through determination of their magnetic properties and through computer modeling. Students involved with this project will learn state-of-the-art techniques in metals synthesis, characterization and theoretical modeling. This project, which combines experimental and theoretical work, will prepare these students for careers in academia (for training our next generation of scientists and engineers) or in industry (where they can apply new techniques for the fabrication of new materials).