Development of a low-temperature insert for the measurement of remanent magnetization direction using superconducting quantum interference device rock magnetometers

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Abstract

Data on the directional changes of a full magnetization vector during cycling to cryogenic temperatures can provide important insights into the low-temperature magnetic properties of natural and synthetic materials. These data also provide an empirical basis for the application of low-temperature treatments in paleomagnetism, for example, the removal of viscous magnetization in magnetite-bearing rocks. However, existing instruments only allow continuous measurement of magnetization along a single axis, hampering experimental and theoretical advances in rock magnetism and the implementation of low-temperature techniques into regular paleomagnetic practices. Here we describe development of a novel low-temperature insert designed in collaboration with William S. Goree Inc., which allows measurement of directional behavior of a full magnetization vector during zero-field low-temperature cycling. Pilot experiments on well-controlled polycrystalline samples of pseudo-single-domain (PSD) and multidomain magnetite as well as on a natural sample containing PSD magnetite indicate that the orientation of a saturation isothermal remanent magnetization (SIRM) imparted at room temperature remains constant during low-temperature cycling to 20 K. This observation lends additional support to low-temperature cycling as a cleaning technique in paleomagnetism. The SIRM imparted in an individual crystal of magnetite showed systematic, albeit small changes upon both cooling and warming through the Verwey temperature, which may reflect switching between the easy magnetization directions. However, the switching effect may be significantly attenuated by crystallographic twinning in magnetite below the transition. Overall, our results demonstrate the potential of the directional low-temperature magnetometry for the advancement of our understanding of the properties of natural and synthetic materials.

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