Giant Skyrmions Stabilized by Dipole-Dipole Interactions in Thin Ferromagnetic Films

Motivated by a recent magnetization reversal experiment on a TbFeCo thin film, we study a topological excitation in the anisotropic nonlinear sigma model together with the Zeeman and magnetic dipole-dipole interactions. Dipole-dipole interactions turn a ferromagnet into a frustrated spin system, which allows a nontrivial spin texture such as a giant Skyrmion. We derive an analytic formula for the Skyrmion radius. The radius is controllable by the external magnetic field. It is intriguing that a Skyrmion may have already been observed as a magnetic domain. A salient feature is that a single Skyrmion can be created or destroyed experimentally. An analysis is made also on Skyrmions in chiral magnets.

受近期在TbFeCo薄膜上进行的磁化反转实验的启发，我们研究了各向异性非线性σ模型中的拓扑激发以及塞曼相互作用和磁偶极 - 偶极相互作用。偶极 - 偶极相互作用将铁磁体转变为一个受挫的自旋系统，这使得诸如巨型斯格明子（Skyrmion）这样的非平凡自旋织构得以存在。我们推导出了斯格明子半径的解析公式。该半径可由外磁场控制。有趣的是，斯格明子可能已经作为一个磁畴被观测到。一个显著的特征是，单个斯格明子可以通过实验产生或消除。我们还对手性磁体中的斯格明子进行了分析。