The Besnus transition in 4C pyrrhotite revisited

SUMMARY Ferrimagnetic, monoclinic 4C pyrrhotite (Fe7S8) is the only iron sulphide with high relevance for palaeomagnetism and rock magnetism that can be identified in materials by its characteristic low-temperature anomaly. Despite natural many magnetic studies over last decades, physics crystallography behind this anomaly, also denoted Besnus transition, a matter of debate. In study, we analyse static dynamic magnetization associated transition conjunction structural data reported literature. The correlation between Fe–Fe bonds causing spin-orbit coupling properties show characteristics stem from interaction two magnetocrystalline anisotropy systems triggered thermally induced changes on an atomic level pyrrhotite. This refutes widespread view caused crystallographic change to triclinic.