Understanding dipolar magnetostatic interactions in bulk natural samples with extended first-order reversal curve (FORC) diagrams

Natural samples generally contain complex magnetic mineral assemblages. Magnetostatic dipole-dipole interactions among particles strongly affect magnetic hysteresis behavior and magnetic recording fidelity, which makes it important to understand magnetostatic interactions in natural samples. Henkel-plots or deltaM curves are often used to examine interactions in bulk samples in materials science applications; FORC diagrams are also used to investigate interactions among single domain (SD) magnetic particles in bulk samples. However, each method has their own limitations; the former are more suitable for samples with narrow grain size distributions, while the later has difficulty in discriminating dipolar interactions from internal interactions in non-SD particles (e.g., due to domain wall interactions or vortex nucleation/annihilation). We explore here an approach to develop a better understanding of dipolar magnetostatic interactions in natural samples using extended FORC measurements that enable disentangling of ambiguities associated with discriminating interactions in conventional FORC diagrams.