Ricci Fabio, Bousquet Eric
Physique Théorique des Matériaux, Université de Liège, B-4000 Sart Tilman, Belgium.
Phys Rev Lett. 2016 Jun 3;116(22):227601. doi: 10.1103/PhysRevLett.116.227601.
We report on a first-principles study of the troilite phase of iron sulfide (FeS). We show that even if, a few decades ago, this material was thought to be ferroelectric, the structural transition from the high P6_{3}/mmc to the low P6[over ¯]2c symmetry phase does not involve polar instabilities, though the space inversion center symmetry is broken. Our calculations and symmetry analysis nevertheless reveal that FeS is magnetoelectric at room temperature with a response larger than the prototypical room-temperature magnetoelectric crystal Cr_{2}O_{3}. We also show that the spin channel decomposition of the polarization exhibits nonzero values in the opposite direction in FeS, which is actually a general hint of the presence of a magnetoelectric monopole in diagonal magnetoelectrics.
我们报道了对硫化铁（FeS）陨硫铁相的第一性原理研究。我们表明，即使几十年前这种材料被认为是铁电体，但从高对称的P6₃/mmc到低对称的P6[上划线]2c结构转变并不涉及极性不稳定性，尽管空间反演中心对称性被打破。然而，我们的计算和对称性分析表明，FeS在室温下是磁电体，其响应比典型的室温磁电晶体Cr₂O₃更大。我们还表明，在FeS中极化的自旋通道分解在相反方向呈现非零值，这实际上是对角磁电体中存在磁电单极子的一个普遍迹象。
