RUI: Magnetic Phase Transitions in Intercalated Dichalcogenides

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****Technical Abstract****Transition-metal dichalcogenides such as titanium disulfide possess a layered crystal structure consisting of atomic trilayers stacked along the c axis. The trilayers are weakly bound by van der Waals forces. Pure dichalcogenides exhibit interesting properties such as charge density waves and superconductivity. Foreign atoms can be introduced into the interlayer gaps; this is called intercalation. In this project, the effects of intercalating magnetic ions on the properties of dichalcogenide materials will be experimentally investigated. By varying the type and content of the intercalant and the nature of the host, competition between magnetic phases will be controlled and transitions between phases studied. Quasi-one-dimensional nanostructures will also be fabricated and studied. The outcome of the project is a better understanding of how structure and interactions determine magnetic ground states in the dichalcogenides and other materials such as manganites. Undergraduates will be deeply involved in sample fabrication, measurements and data analysis. The efficacy of undergraduate research for training students in scientific reasoning and writing will be assessed using nationally recognized instruments. High-school students from underrepresented groups will also be immersed and mentored in the research environment.****Non-Technical Abstract****Transition-metal dichalcogenides (for example, titanium disulfide) have a crystal structure consisting of layers of atoms (three atoms thick) stacked along a direction perpendicular to the layers. The layers are weakly bonded, which permits the introduction of new atoms between the layers in a process called intercalation. The intercalated material has properties that reflect both those of the host and the inserted atoms. Thus, one can control the overall properties of the material by controlling the type and number of intercalant atoms. Such tunable materials could be very useful in new magnetic and electronic devices in which specific characteristics could be engineered by controlling the properties of the intercalant. This project will investigate a variety of intercalated dichalcogenides, including newly fabricated nanotubes. Magnetic and electronic properties will be carefully measured to obtain a thorough understanding of the behavior of these materials. Their potential for applications will then be evaluated. Undergraduate students will play an integral part in every aspect of the research. The efficacy of undergraduate research for training students in scientific reasoning and writing will be assessed. High-school students from underrepresented groups will also be immersed and mentored in the research environment.