Low-iron polymorphs in the pyrrhotite group

Abstract

Two naturally-occurring low-iron pyrrhotite superstructures, based on the NiAs structure, have been confirmed. High-temperature precession photographs show that the transformation from the 4 C structure to the NiAs structure occurs at 225 ± 10°C and is unrelated to the magnetic transition above 300°C. A new superstructure, also based on the NiAs structure, has been produced by quenching.