A wide variety of Earth and planetary materials are very good recorders of paleomagnetic
information. However, most magnetic grains in these materials are not in the stable single
domain grain size range but are larger and in nonuniform vortex magnetization states. We
provide a detailed account of vortex phenomena in geologic materials by simulating first‐
order reversal curves (FORCs) via finite‐element micromagnetic modeling of magnetite
nanoparticles with realistic morphologies. The particles have been reconstructed from …

Rocks can record information about the geomagnetic field intensity and direction, 37 and
preserve it over geologic timescales. Uniformly magnetized, stable single domain 38 (SD)
particles are ideal recorders of this information [Néel, 1949], and rock magnetic 39 recording
mechanisms are widely tied to their presence in natural materials. For mag-40 netite, SD
grains are usually a few tens of nm in size in the case of equidimensional parti-41 cles, and
up to 200 nm for elongated particles. Slightly larger particles have non-uniform 42 …