MI2023 - 06 Lesleis Nagy: Insights from micromagnetic modeling for thermomagnetic recording
Channel: MagNetZ
Date: 16/01/2023

Magnetic Interactions 2023 conference at the University of Cambridge
Session 2: Rock and Mineral Magnetism

Title: Chasing tails: Insights from micromagnetic modeling for thermomagnetic recording in non-uniform magnetic structures
Author: Lesleis Nagy from the University of Liverpool, UK

Paleointensities are key to understanding the formation and evolution of Earth and are determined from rocks which record magnetic fields upon cooling; however, experimental protocols for estimating paleointensities frequently fail. The primary reason is that laboratory protocols assume that rocks are dominated by uniformly magnetized, single-domain grains, instead of much more common non-uniformly magnetized grains. Our model for larger grains shows a multiplicity of stable domain states; with preferred states changing as a function of temperature. We show that domain state distribution depends on the thermal history of the sample—in nature and the laboratory. From numerical thermomagnetic modelling, we show that particles with non-uniform domain states will theoretically fail standard experimental paleointensity protocols, preventing us from determining reliable ancient geomagnetic field intensities. We propose that recognizing this type of behaviour, and the resulting bias, will yield more reliable paleointensity records, and a better understanding of the Earth.

-----------------------------------------------------------

00:00 - Intro
00:26 - Presentation
14:40 - Questions