Many natural magnetic minerals undergo transitions at low temperature. Scientists investigating the history of Earth's magnetic 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 to monoclinic) at approximately 120 K known as the Verwey transition. A loss of the magnetic remanence carried by relatively large magnetite grains is also observed at the transition. However, our understanding of this process, as well as processes associated with transitions in other natural magnetic minerals, has to date been based mainly on measurements of total magnetic moment. A prototype device enabling the measurement of directions with a SQUID magnetometer during cooling/warming through low temperature transitions suggests interesting phenomena, possibly related to the interactions of magnetic domain walls and crystal deflects. The PI will test this hypothesis, compile new directional data on a wide range of magnetic minerals, and continue to develop the device for low temperature cooling/directional analysis. Broader impacts of the work include educational efforts and the development of a research tool useful for the rock magnetism and paleomagnetism communities (and the community in physics interested in magnetic properties at low temperatures). Undergraduates will take part in the characterization of magnetic minerals, low temperature remanence measurements and data analyses.
