标题： 在kagome磁体（Co$_{0.45}$Fe$_{0.55}$)Sn中反铁磁性和局部对称性破缺的同时发展 显示英文标题

标题： Simultaneous development of antiferromagnetism and local symmetry breaking in a kagome magnet (Co$_{0.45}$Fe$_{0.55}$)Sn

摘要： CoSn和FeSn两种kagome晶格金属最近因其电子平带和出现的物理特性而受到广泛关注。然而，目前对其物理特性的理解仅限于平均晶体结构的知识。在这里，我们报告了在（Co0.45Fe0.55）Sn中，铁掺杂诱导的反铁磁（AFM）序和局部对称性破缺的同时出现。中子和同步辐射X射线衍射数据的Rietveld分析表明，具有磁矩垂直于kagome层的A型反铁磁序，与MSn(1)2Sn(2)4（M = Co/Fe）八面体畸变和晶格常数c的异常相关。同步辐射X射线总散射结果的逆蒙特卡罗（RMC）建模捕捉到了涉及Sn2偏离轴位移的微小局部正交畸变。我们的结果表明，高于TN的稳定六方晶格在TN以下形成A型AFM序后变得不稳定。我们认为局部对称性破缺具有磁性起源，并由面外磁交换耦合驱动。我们的研究提供了长程尺度和局部尺度上的晶体结构综合信息，揭示了AFM序、八面体畸变和隐藏局部对称性破缺之间的独特耦合。 显示英文摘要

摘要： CoSn and FeSn, two kagome-lattice metals, have recently attracted significant attention as hosts of electronic flat bands and emergent physical properties. However, current understandings of their physical properties are limited to the knowledge of the average crystal structure. Here, we report the Fe-doping induced co-emergence of the antiferromagentic (AFM) order and local symmetry breaking in (Co0.45Fe0.55)Sn. Rietveld analysis on the neutron and synchrotron x-ray diffraction data indicates A-type antiferromagnetic order with the moment pointing perpendicular to the kagome layers, associated with the anomaly in the MSn(1)2Sn(2)4 (M = Co/Fe) octahedral distortion and the lattice constant c. Reverse Monte Carlo (RMC) modeling of the synchrotron x-ray total scattering results captured the subtle local orthorhombic distortion involving off-axis displacements of Sn2. Our results indicate that the stable hexagonal lattice above TN becomes unstable once the A-type AFM order is formed below TN. We argue that the local symmetry breaking has a magnetic origin and is driven by the out-of-plane magnetic exchange coupling. Our study provides comprehensive information on the crystal structure in both long-range scale and local scale, unveiling unique coupling between AFM order, octahedral distortion, and hidden local symmetry breaking.