Liu Jieyi, Yang Yiheng, Shen Jianlei, Liu Defa, Thakur Gohil Singh, Guillemard Charles, Smekhova Alevtina, Chen Houke, Biswas Deepnarayan, Valvidares Manuel, Liu Enke, Felser Claudia, Lee Tien-Lin, Hesjedal Thorsten, Chen Yulin, van der Laan Gerrit
Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K.
Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, U.K.
ACS Nano. 2025 Mar 11;19(9):8561-8570. doi: 10.1021/acsnano.4c13750. Epub 2025 Feb 25.
The physical properties of magnetic topological materials are strongly influenced by their nontrivial band topology coupled with the magnetic structure. CoSnS is a ferromagnetic kagome Weyl semimetal displaying giant intrinsic anomalous Hall effect which can be further tuned via elemental doping, such as Ni substitution for Co. Despite significant interest, the exact valency of Co and the magnetic order of the Ni dopants remained unclear. Here, we report a study of Ni-doped CoSnS single crystals using synchrotron-based X-ray magnetic circular dichroism (XMCD), X-ray photoelectron emission microscopy (XPEEM), and hard/soft X-ray photoemission spectroscopy (XPS) techniques. We confirm the presence of spin-dominated magnetism from Co in the host material, and also the establishment of ferromagnetic order from the Ni dopant. The oxygen-free photoemission spectrum of the Co 2p core levels in the crystal well resembles that of a metallic Co film, indicating a Co valency. Surprisingly, we find the electron filling in the Co 3d state can reach 8.7-9.0 electrons in these single crystals. Our results highlight the importance of element-specific X-ray spectroscopy in understanding the electronic and magnetic properties that are fundamental to a heavily studied Weyl semimetal, which could aid in developing future spintronic applications based on magnetic topological materials.
磁性拓扑材料的物理性质受到其非平凡能带拓扑结构与磁结构耦合的强烈影响。CoSnS是一种铁磁卡戈梅外尔半金属，表现出巨大的本征反常霍尔效应，可通过元素掺杂（如用Ni替代Co）进一步调节。尽管人们对此兴趣浓厚，但Co的精确化合价和Ni掺杂剂的磁序仍不明确。在此，我们报告了一项使用基于同步加速器的X射线磁圆二色性（XMCD）、X射线光电子发射显微镜（XPEEM）以及硬/软X射线光电子能谱（XPS）技术对Ni掺杂CoSnS单晶进行的研究。我们证实了主体材料中Co存在自旋主导的磁性，以及Ni掺杂剂形成的铁磁序。晶体中Co 2p芯能级的无氧光发射光谱与金属Co薄膜的光谱非常相似，表明了Co的化合价。令人惊讶的是，我们发现这些单晶中Co 3d态的电子填充数可达8.7 - 9.0个电子。我们的结果突出了元素特异性X射线光谱学在理解一种经过大量研究的外尔半金属的基本电子和磁性性质方面的重要性，这有助于开发基于磁性拓扑材料的未来自旋电子学应用。
