Study of Anomalous Magnetism and Superconductivity in Selected Lanthanides, Alkalis and Noble Metals Under Extreme Pressure

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Non-Technical AbstractWhereas simple materials are easier to understand, complex materials are more interesting and more likely to lead to innovative applications. In this single investigator award extremely high pressures, as high as 2-3 million atmospheres, are applied to very simple and soft materials, like the alkali metals. Such extreme pressures are able to continuously transform these metals into surprisingly complex materials that may become superconducting, ferromagnetic or even insulating. The fact that a single sample can be brought through extreme compression to exhibit such anomalous behavior allows one to gain a deeper understanding of what makes them tick. This enhanced understanding, on the other hand, facilitates the design of materials with useful properties at ambient pressure. In elements called "rare-earths", high pressures have been found to induce magnetic ordering at very high temperatures. With some luck this work could lead to the development of superior permanent magnets, a ubiquitous material in everyday life. The proposed experiments give undergraduate and graduate students the opportunity to learn and develop a multitude of essential experimental techniques; these students also benefit from scientific collaborations with groups both in the US and abroad.Technical AbstractThe research in this single investigator award has two primary thrust directions. The first is the transformation under extreme compression of canonical simple free-electron metals, such as the alkali metals, into materials with highly anomalous electronic properties. These properties include superconductivity at relatively high temperatures, metal-semiconductor or metal-insulator transitions or even Pauli paramagnetic to itinerant ferromagnetic transitions. This project will study in depth to ultrahigh pressures the superconducting phase diagram and critical magnetic field behavior of selected alkali metals as well as their alloys and compounds. The second thrust direction has evolved out of the discovery by the PI's group of magnetic order at temperatures well above ambient in selected lanthanides under extreme pressures. This raises the possibility of a permanent magnet material superior to the current record holder Nd-Fe-B. Further materials of interest are the hydrides, particularly following the very recent discovery of superconductivity in sulfur dihydride near 190 K. The proposed experiments give undergraduate and graduate students an excellent opportunity to learn and develop important laboratory techniques and collaborate with groups both in the US and abroad.