空中骑兵
螺旋度
物理
磁畴
凝聚态物理
磁场
磁螺旋度
洛伦兹变换
拓扑(电路)
磁化
经典力学
量子力学
磁流体力学
组合数学
数学
作者
Xiuzhen Yu,Maxim Mostovoy,Y. Tokunaga,Weizhu Zhang,Koji Kimoto,Yoshio Matsui,Y. Kaneko,Naoto Nagaosa,Yoshinori Tokura
标识
DOI:10.1073/pnas.1118496109
摘要
It was recently realized that topological spin textures do not merely have mathematical beauty but can also give rise to unique functionalities of magnetic materials. An example is the skyrmion—a nano-sized bundle of noncoplanar spins—that by virtue of its nontrivial topology acts as a flux of magnetic field on spin-polarized electrons. Lorentz transmission electron microscopy recently emerged as a powerful tool for direct visualization of skyrmions in noncentrosymmetric helimagnets. Topologically, skyrmions are equivalent to magnetic bubbles (cylindrical domains) in ferromagnetic thin films, which were extensively explored in the 1970s for data storage applications. In this study we use Lorentz microscopy to image magnetic domain patterns in the prototypical magnetic oxide–M-type hexaferrite with a hint of scandium. Surprisingly, we find that the magnetic bubbles and stripes in the hexaferrite have a much more complex structure than the skyrmions and spirals in helimagnets, which we associate with the new degree of freedom—helicity (or vector spin chirality) describing the direction of spin rotation across the domain walls. We observe numerous random reversals of helicity in the stripe domain state. Random helicity of cylindrical domain walls coexists with the positional order of magnetic bubbles in a triangular lattice. Most unexpectedly, we observe regular helicity reversals inside skyrmions with an unusual multiple-ring structure.
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