Institute of Engineering Innovation, School of Engineering, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan.
Department of Materials Science and Engineering, Graduate School of Engineering and Resource Science, Akita University, 1-1 Tegata Gakuen-machi, Akita, Akita 010-8502, Japan.
Sci Adv. 2016 Feb 12;2(2):e1501280. doi: 10.1126/sciadv.1501280. eCollection 2016 Feb.
Skyrmions are topologically protected nanoscale magnetic spin entities in helical magnets. They behave like particles and tend to form hexagonal close-packed lattices, like atoms, as their stable structure. Domain boundaries in skyrmion lattices are considered to be important as they affect the dynamic properties of magnetic skyrmions. However, little is known about the fine structure of such skyrmion domain boundaries. We use differential phase contrast scanning transmission electron microscopy to directly visualize skyrmion domain boundaries in FeGe1-x Si x induced by the influence of an "edge" of a crystal grain. Similar to hexagonal close-packed atomic lattices, we find the formation of skyrmion "Σ7" domain boundary, whose orientation relationship is predicted by the coincidence site lattice theory to be geometrically stable. On the contrary, the skyrmion domain boundary core structure shows a very different structure relaxation mode. Individual skyrmions can flexibly change their size and shape to accommodate local coordination changes and free volumes formed at the domain boundary cores. Although atomic rearrangement is a common structural relaxation mode in crystalline grain boundaries, skyrmions show very unique and thus different responses to such local lattice disorders.
螺旋磁体中的斯格明子是拓扑保护的纳米尺度磁性自旋实体。它们的行为类似于粒子，并倾向于形成六方密堆积晶格，就像原子一样，作为它们的稳定结构。由于斯格明子晶格的畴界会影响磁性斯格明子的动力学特性，因此被认为是重要的。然而，对于这种斯格明子畴界的精细结构知之甚少。我们使用微分相衬扫描透射电子显微镜直接观察到由晶粒“边缘”影响在 FeGe1-xSix 中诱导的斯格明子畴界。类似于六方密堆积的原子晶格，我们发现斯格明子“Σ7”畴界的形成，其取向关系由重合位置晶格理论预测为几何稳定的。相反，斯格明子畴界核心结构表现出非常不同的结构弛豫模式。单个斯格明子可以灵活地改变其大小和形状，以适应畴界核心处的局部配位变化和形成的自由体积。虽然原子重排是晶界中常见的结构弛豫模式，但斯格明子对这种局部晶格无序表现出非常独特的、因此不同的响应。
