Single particle multipole expansions from Micromagnetic Tomography

TL;DR

This paper introduces a mathematical method to recover higher-order magnetic potential details of individual particles using spherical harmonic expansions, enhancing the analysis of magnetic structures in rock samples.

Contribution

It presents a novel mathematical procedure to extract higher-order multipole moments from magnetic particle data, improving the detail and reliability of micromagnetic tomography.

Findings

SHE up to order n=3 can be robustly recovered for high SNR data.

The method provides insights into internal magnetization structures.

Enhanced magnetic detail aids in rock magnetic studies.

Abstract

Micromagnetic tomography aims at reconstructing large numbers of individual magnetizations of magnetic particles from combining high-resolution magnetic scanning techniques with micro X-ray computed tomography (microCT). Previous work demonstrated that dipole moments can be robustly inferred, and mathematical analysis showed that the potential field of each particle is uniquely determined. Here, we describe a mathematical procedure to recover higher orders of the magnetic potential of the individual magnetic particles in terms of their spherical harmonic expansions (SHE). We test this approach on data from scanning superconducting quantum interference device microscopy and microCT of a reference sample. For particles with high signal-to-noise ratio of the magnetic scan we demonstrate that SHE up to order $n=3$ can be robustly recovered. This additional level of detail restricts the possible internal magnetization structures of the particles and provides valuable rock magnetic information with respect to their stability and reliability as paleomagnetic remanence carriers. Micromagnetic tomography therefore enables a new approach for detailed rock magnetic studies on large ensembles of individual particles.