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.

磁黄铁矿（Pyrrhotite，化学式Fe₇S₈）是一种天然产出的矿物，因其显著的剩余磁化强度而受到研究关注。该矿物在约600 K时会经历NiAs-4C型（六方-单斜）结构相变，该相变同时对应其亚铁磁相变。此结构相变会诱发铁弹性畴（或称"孪晶"）的形成。本研究计划开展以下工作：验证室温下施加磁场不会改变铁弹性畴的状态；确认铁弹性畴会在奈尔温度（Néel temperature）以上完全消失；探究铁弹性畴重组过程中的动力学行为；量化磁弹性效应的强弱；并研究孪晶畴的取向随应变的变化规律。