Tuning the structure-property relationships in intermetallic superconductors and magnetic systems with chemical doping

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Nontechnical abstract:This research focuses on an experimental investigation of the magnetic and transport properties of certain intermetallic compounds that display bulk magnetism or superconductivity. The physical properties of the materials being studied are intimately tied to their crystal structures and underlying symmetries. In fact, the growing body of recent research in condensed matter physics shows the importance in understanding a material’s topology. The synthesis of high quality single crystals is an important component of this project, and chemical doping is used to tune the material’s physical properties. This research is integrated into an educational plan to enhance both graduate and undergraduate learning in the laboratory and classroom. A productive K-12 outreach effort targets pre-college minority students and utilizes professors, graduate students, and education majors in physics. This experimental research provides graduate and undergraduate students with valuable experience and training in the areas of materials synthesis, structural characterization, measurement of physical properties, data acquisition, and analysis. In addition to synthesis and characterization experience, the undergraduate researcher learns basic laboratory skills and receives training in techniques of low-temperature physics. Finally, single crystal growth and the synthesis of new materials help the United States to maintain a significant presence in a highly competitive global materials effort. Technical abstract:This research focuses on superconductors, impurity band ferromagnets, and new materials formed under high pressure, where the salient features of the physics in these systems are driven by their structure/property relationships. The level of chemical and structural disorder is controlled through doping, and variable stoichiometry provides the ability to probe the material’s phase space. The recent discovery by the principle investigator’s research group of a Dirac surface state in the electronic structure of BiPd and the existence of a nontrivial pi-Berry phase in one of its bulk bands provide the motivation for further study. In particular, the synthesis in reduced dimensions, along with the effects of hole doping, is explored. Second, the discovery of a ferromagnetic quantum critical point in electron-doped FeGa3 suggests the preservation of a novel structural feature (Fe-Fe dimers) is important for the stability of long-range order. Interesting magnetic ground states observed in FeGa3 doped with Ru and Mn are thoroughly explored. In addition to studying compounds related to FeGa3, the PI focuses on other materials containing boron or carbon dimers. Finally, high-pressure synthesis capabilities are used to search for new superconductors in the boride and carbide all-metal perovskite family of compounds. The experimental results obtained from this research aid in understanding of strongly correlated electron systems in general. This research offers the opportunity for new materials discovery, as well as trains the next generation of materials scientists in multiple techniques of single crystal growth and physical properties characterization.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.