Acquisition of SQUID Magnetometer - Susceptometer with Resistivity and Hall Effect Measurement Option

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9318333 Schweitzer The SQUID magnetometer with AC susceptibility, resistivity, and Hall effect measurement capabilities will be used to study the electrical transport and magnetic properties of layered sulfide alloys. The research project will investigate the unusual metal- insulator transition thansition that we have recently discovered in the BaCo1-xNixS2-y system. This first-order phase transition is from a semiconducting to a metallic phase with decreasing temperature. The low temperature phase is a highly correlated metal, while the high temperature phase appears to be a two- dimensional antiferromagnet. The transition temperature and hysteresis depend on the chemical composition. The thermal bistability and positive temperature coefficient of resistivity associated with the transition suggest that these materials could be useful for many practical applications in materials research and engineering. The large resistance change at the transition, the ability to control the properties by varying the composition, and the stability of the materials are all favorable for applications. %%% The experimental program will also involve exploratory synthesis and characterization of related ternary sulfide and selenide alloys that might exhibit similar phenomena or possibly superconductivity. The equipment requested will be used to measure the DC magnetization, AC magnetic susceptibility, resistivity, and Hall coefficient of all phases found. The existence of this unusual phase transition in certain layered ternary sulfides is a significant discovery of previously unknown phenomena. Study of these materials can contribute to our understanding of highly correlated electronic systems, metal- insulator transitions, and perhaps high temperature superconductivity. ***