Topological magnetic textures and long-range orders in terbium-based quasicrystal and approximant
Topological magnetic textures and long-range orders in terbium-based quasicrystal and approximant
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DOI：
10.1073/pnas.2112202118
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发表时间：
2021-10-26
影响因子：
11.1
通讯作者：
Watanabe, Shinji
中科院分区：
文献类型：
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作者：
Watanabe, Shinji
准晶体（QC）具有独特的晶格结构，具有周期晶体中禁止的旋转对称性。电特性还远未完全了解。 QC中能否实现磁性远程有序一直是一个长期存在的问题。在这里，我们报告了基于 Tb 的 QC 中铁磁长程有序的理论发现。过去QC理论研究的困难在于缺乏晶体电场（CEF）的微观理论，而这在稀土系统中至关重要。通过分析 Tb 基 QC 中的 CEF，我们阐明磁各向异性在实现 Tb 基 QC 和近似晶体 (AC) 中独特的磁织构中起着关键作用。通过构建最小模型，我们证明了在二十面体上实现了各种磁性纹理，其顶点为 Tb 原子。我们发现刺猬态的特征是拓扑电荷为1，而旋转矩态的特征是异常大的拓扑电荷为3。刺猬态和旋转矩态被证明是作为反铁磁级实现的，转录为 1/1 AC 中的涌现单极子和反单极子。我们发现这些态在外加磁场下表现出拓扑霍尔效应，并伴有拓扑和变磁转变。我们的模型和确定的相图预计与具有强磁各向异性的稀土基QC和AC相关，这不仅有助于理解磁性，而且有助于探索拓扑性质。
The quasicrystal (QC) possesses a unique lattice structure with rotational symmetry forbidden in periodic crystals. The electric property is far from complete understanding. It has been a long-standing issue whether magnetic long-range order is realized in the QC. Here, we report our theoretical discovery of the ferromagnetic long-range order in the Tb-based QC. The difficulty in past theoretical studies on the QC was lack of the microscopic theory of the crystalline electric field (CEF), which is crucially important in the rare earth systems. By analyzing the CEF in the Tb-based QC, we clarify that magnetic anisotropy plays a key role in realizing unique magnetic textures in the Tb-based QC and approximant crystal (AC). By constructing the minimal model, we show that various magnetic textures on the icosahedron, at whose vertices Tb atoms are located, are realized. We find that the hedgehog state is characterized by the topological charge of one and the whirling-moment state is characterized by an unusually large topological charge of three. The hedgehog and whirling-moment states are shown to be realized as antiferromagnetic orders transcribed as the emergent monopole and antimonopole in the 1/1 AC. We find that these states exhibit the topological Hall effect under applied magnetic field accompanied by the topological as well as metamagnetic transition. Our model and the determined phase diagram are expected to be relevant to the broad range of the rare earth-based QCs and ACs with strong magnetic anisotropy, which are useful not only to understand magnetism but also, to explore topological properties.