Tokura Yoshinori, Kanazawa Naoya
Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan.
RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan.
Chem Rev. 2021 Mar 10;121(5):2857-2897. doi: 10.1021/acs.chemrev.0c00297. Epub 2020 Nov 8.
Skyrmion, a concept originally proposed in particle physics half a century ago, can now find the most fertile field for its applicability, that is, the magnetic skyrmion realized in helimagnetic materials. The spin swirling vortex-like texture of the magnetic skyrmion can define the particle nature by topology; that is, all the constituent spin moments within the two-dimensional sheet wrap the sphere just one time. Such a topological nature of the magnetic skyrmion can lead to extraordinary metastability via topological protection and the driven motion with low electric-current excitation, which may promise future application to spintronics. The skyrmions in the magnetic materials frequently show up as the crystal lattice form, e.g., hexagonal lattice, but sometimes as isolated or independent particles. These skyrmions in magnets were initially found in acentric magnets, such as chiral, polar, and bilayered magnets endowed with antisymmetric spin exchange interaction, while the skyrmion host materials have been explored in a broader family of compounds including centrosymmetric magnets. This review describes the materials science and materials chemistry of magnetic skyrmions using the classification scheme of the skyrmion forming microscopic mechanisms. The emergent phenomena and functions mediated by skyrmions are described, including the generation of emergent magnetic and electric field by statics and dynamics of skrymions and the inherent magnetoelectric effect. The other important magnetic topological defects in two or three dimensions, such as biskyrmions, antiskyrmions, merons, and hedgehogs, are also reviewed in light of their interplay with the skyrmions.
斯格明子，这个概念半个世纪前最初在粒子物理学中被提出，如今却能找到其适用性最为广阔的领域，即螺旋磁体材料中实现的磁性斯格明子。磁性斯格明子的自旋呈涡旋状纹理，可通过拓扑结构定义其粒子性质；也就是说，二维平面内所有组成自旋矩仅环绕球体一次。磁性斯格明子的这种拓扑性质可通过拓扑保护和低电流激发下的驱动运动导致非凡的亚稳性，这或许有望在未来应用于自旋电子学。磁性材料中的斯格明子常以晶格形式出现，如六角晶格，但有时也表现为孤立或独立的粒子。磁体中的这些斯格明子最初是在非中心对称磁体中发现的，比如具有反对称自旋交换相互作用的手性、极性和双层磁体，而斯格明子主体材料已在包括中心对称磁体在内的更广泛化合物家族中被探索。本综述使用斯格明子形成微观机制的分类方案描述了磁性斯格明子的材料科学和材料化学。描述了由斯格明子介导的涌现现象和功能，包括斯格明子的静态和动态产生的涌现磁场和电场以及固有磁电效应。还根据它们与斯格明子的相互作用对二维或三维中的其他重要磁性拓扑缺陷，如双斯格明子、反斯格明子、磁单极子和刺猬磁畴进行了综述。
