标题： 二维FeXZ$_{2}$（\textit{X}= Nb，Ta和\textit{Z}= S，Se，Te）铁磁体中的复杂磁交换、各向异性和斯格明子纹理 显示英文标题

标题： Complex magnetic exchange, anisotropy and skyrmionic textures in two-dimensional FeXZ$_{2}$ (\textit{X} = Nb, Ta and \textit{Z} = S, Se, Te) ferromagnets

摘要： FeNbTe$_{2}$，长期以来被认为是一种范德华金属系统，最近被重新合成并表现出铁磁有序。 在本研究中，我们使用第一性原理密度泛函理论（DFT），旨在深入探讨FeNbTe$_{2}$及其相关化合物（FeXZ$_{2}$，\textit{X} = Nb，Ta；\textit{Z} = S，Se，Te）在二维形式下的磁性特性，包括它们的非中心对称Janus对应物。 我们的结果表明，这些材料在能量、动态、热和机械方面都是稳定的，支持FeNbTe$_{2}$的剥离可能性以及新化合物实验实现的潜力。 进化结构搜索表明，FeNbTe$_{2}$在单层形式下保持其单斜对称性。 我们对从DFT能带进行Wannier化获得的跃迁参数的分析显示，最近邻的磁相互作用主要是直接的，而次近邻及更远的相互作用则由硫属元素原子介导。 有趣的是，尽管次近邻相互作用的幅度较小，但它们似乎在确定这些系统的磁序中起着关键作用。 我们还发现了FeXZ$_{2}$化合物中倾斜磁各向异性，具有相对较强的磁晶各向异性能量和高达41$^\circ$的易轴偏离，相对于面外方向而言——这在自旋电子学应用中是一种不常见且可能有用的特性。 从蒙特卡洛模拟估算的居里温度低于室温但高于低温水平。 微磁模拟显示，Janus结构的FeNbSeTe即使在没有外部磁场的情况下也能容纳Néel型斯格明子，使该化合物成为进一步实验研究的合适候选。 显示英文摘要

摘要： FeNbTe$_{2}$, long known as a van der Waals metallic system, has recently been resynthesized and shown to exhibit ferromagnetic order. In this study, using first-principles density functional theory (DFT), we aim to provide a deeper insight into the magnetic properties of FeNbTe$_{2}$ and its related compounds (FeXZ$_{2}$, \textit{X} = Nb, Ta; \textit{Z} = S, Se, Te), in their two-dimensional form, including their non-centrosymmetric Janus counterparts. Our results indicate that these materials are energetically, dynamically, thermally, and mechanically stable, supporting the possibility of FeNbTe$_{2}$ exfoliation and potential for experimental realization of new compounds. An evolutionary structure search suggests that FeNbTe$_{2}$ retains its monoclinic symmetry in the monolayer form. Our analysis of hopping parameters obtained from Wannierization of DFT bands shows that the nearest-neighbor magnetic interactions are primarily direct, while second-nearest and more distant interactions are mediated by the chalcogen atoms. Interestingly, although the second-nearest-neighbor interactions are smaller in magnitude, they appear to play a key role in determining the magnetic ordering in these systems. We also find evidence of canted magnetic anisotropy in FeXZ$_{2}$ compounds, with relatively strong magnetocrystalline anisotropy energy and easy-axis deviations of up to 41$^\circ$ from the out-of-plane direction-an uncommon and potentially useful feature for spintronic applications. Curie temperatures estimated from Monte Carlo simulations are below room temperature but above cryogenic levels for most compounds. Micromagnetic simulations revealed that Janus-structured FeNbSeTe can host N\'eel-type skyrmions even in the absence of an external magnetic field, making this compound a suitable candidate for further experimental studies.