Directional Behavior of Remanent Magnetizations at Low Temperatures

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Many natural magnetic minerals undergo transitions at lowtemperature. Scientists investigating the history of Earth'smagnetic field sometimes use such transitions to help demagnetize rocks,removing magnetizations acquired after rock formation. For example,magnetite undergoes a change in crystal structure (from orthorhombic tomonoclinic) at approximately 120 K known as the Verwey transition. Aloss of the magnetic remanence carried by relatively large magnetitegrains is also observed at the transition. However, our understanding ofthis process, as well as processes associated with transitions in othernatural magnetic minerals, has to date been based mainly on measurements oftotal magnetic moment. A prototype device enabling the measurement ofdirections with a SQUID magnetometer during cooling/warming throughlow temperature transitions suggests interesting phenomena,possibly related to the interactions of magnetic domain walls andcrystal deflects. The PI will test this hypothesis, compile new directionaldata on a wide range of magnetic minerals, and continue to develop the devicefor low temperature cooling/directional analysis. Broader impacts of thework include educational efforts and the development of a research tooluseful for the rock magnetism and paleomagnetism communities (and thecommunity in physics interested in magnetic properties at low temperatures).Undergraduates will take part in the characterization of magneticminerals, low temperature remanence measurements and data analyses.