Magnetoelastic coupling between ferroelastic twins and ferromagnetic moments in pyrrhotite

Pyrrhotite, Fe7S8, is a naturally occurring mineral of interest because of its large remnant magnetisation. It goes through a NiAs-4C (hexagonal-monoclinic) structural phase transition at approximately 600 K that also corresponds to its ferrimagnetic phase transition. This structural phase transition causes the onset of ferroelastic domains or ‘twins’. In this study, we plan to confirm that ferroelastic domains are unchanged by applying a magnetic field at room temperature, that they disappear above the Néel temperature and study their dynamics as they reform, quantify the degree of magnetoelasticity and study the reorientation of the twin domains as a function of strain.