Magnetic Hysteresis Properties of Magnetite: Trends With Particle Size and Shape

Magnetic hysteresis measurements are routinely made in the Earth and planetary sciences to identify geologically meaningful magnetic recorders, and to study variations in present and past environments. Interpreting magnetic hysteresis data in terms of domain state and paleomagnetic stability are major motivations behind undertaking these measurements, but the interpretations remain fraught with challenges and ambiguities. To shed new light on these ambiguities, we have undertaken a systematic micromagnetic study to quantify the magnetic hysteresis behavior of room‐temperature magnetite as a function of particle size (45–195 nm; equivalent spherical volume diameter) and shape (oblate, prolate and equant); our models span uniformly magnetized single domain (SD) to non‐uniformly magnetized single vortex (SV) states. Within our models the reduced magnetization associated with SV particles marks a clear boundary between SD (≥0.5) and SV (