Büttner Felix, Lemesh Ivan, Beach Geoffrey S D
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA.
Sci Rep. 2018 Mar 13;8(1):4464. doi: 10.1038/s41598-018-22242-8.
Magnetic skyrmions are topological quasiparticles of great interest for data storage applications because of their small size, high stability, and ease of manipulation via electric current. However, although models exist for some limiting cases, there is no universal theory capable of accurately describing the structure and energetics of all skyrmions. The main barrier is the complexity of non-local stray field interactions, which are usually included through crude approximations. Here we present an accurate analytical framework to treat isolated skyrmions in any material, assuming only a circularly-symmetric 360° domain wall profile and a homogeneous magnetization profile in the out-of-plane direction. We establish the first rigorous criteria to distinguish stray field from DMI skyrmions, resolving a major dispute in the community. We discover new phases, such as bi-stability, a phenomenon unknown in magnetism so far. We predict materials for sub-10 nm zero field room temperature stable skyrmions suitable for applications. Finally, we derive analytical equations to describe current-driven dynamics, find a topological damping, and show how to engineer materials in which compact skyrmions can be driven at velocities >1000 m/s.
磁斯格明子是一种拓扑准粒子，因其尺寸小、稳定性高且易于通过电流进行操控，在数据存储应用中备受关注。然而，尽管存在一些针对特定极限情况的模型，但尚无一种通用理论能够准确描述所有斯格明子的结构和能量。主要障碍在于非局部杂散场相互作用的复杂性，通常只能通过粗略近似来纳入考虑。在此，我们提出了一个精确的分析框架，用于处理任何材料中的孤立斯格明子，仅假设具有圆对称的360°畴壁轮廓以及面外方向上的均匀磁化轮廓。我们建立了首个严格标准来区分杂散场斯格明子和DMI斯格明子，解决了该领域的一个主要争议。我们发现了新的相，比如双稳态，这是迄今为止在磁学中未知的一种现象。我们预测了适用于应用的亚10纳米零场室温稳定斯格明子的材料。最后，我们推导了描述电流驱动动力学的解析方程，找到了一种拓扑阻尼，并展示了如何设计材料，使得紧凑的斯格明子能够以大于1000米/秒的速度被驱动。
