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arXiv · 2404.07769

Coupling nanoscopic tomography and micromagnetic modelling to assess the stability of geomagnetic recorders

Ualisson Donardelli Bellon·Wyn Williams·Ricardo Ivan Ferreira Trindade·Ana Diaz·Douglas Galante
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Abstract

The recording of planetary magnetic fields is often attributed to uniformly-magnetised nanoscopic iron oxides, called single-domain (SD). Yet, the main magnetic constituents of rocks are more complex, non-uniformly magnetised grains in single or multi-vortex states. We know little about their behaviour due to limitations in defining their precise shape and internal magnetic structure. We propose a novel approach combining non-destructive synchrotron-based ptychographic nanotomography with micromagnetic modelling to explore the magnetic stability of remanence-bearing minerals. Applied to a microscopic rock sample, we identified hundreds of nanoscopic grains of magnetite/maghemite with diverse morphologies. For some grains, shape irregularities near the transition from SD to the single-vortex state allow for multiple domain states, some unstable and unable to record the field for significant periods. Additionally, some other grains exhibit temperature-dependent occupancy probabilities, potentially hampering experiments to recover the intensity of past magnetic fields.

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Ualisson Donardelli Bellon, Wyn Williams, Ricardo Ivan Ferreira Trindade, Ana Diaz, Douglas Galante. 2024-04-11. Coupling nanoscopic tomography and micromagnetic modelling to assess the stability of geomagnetic recorders. https://arxiv.org/abs/2404.07769

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