标题： 单层$3d$过渡金属二卤化物中磁性的微观起源 显示英文标题

标题： Microscopic origin of magnetism in monolayer $3d$ transition metal dihalides

摘要： 受二维几何阻挫晶格中新兴的奇异磁性相的启发，我们研究了三角晶格材料单层家族$MX_2$（$M$={V，Mn，Ni}，$X$={氯、溴、碘}）中可能磁性的起源。 我们首先表明，考虑填充和杂化等一般性质可以制定最相关的磁相互作用参数的趋势。 特别是，我们观察到自旋-轨道耦合（SOC）的影响可以通过配体元素有效调节，因为所考虑的3$d$过渡金属离子对位间交换相互作用的各向异性分量没有强烈贡献。 因此，我们发现相应的SOC矩阵元与原子极限显著不同。 在下一步中，通过使用两种基于第一性原理的互补方法，我们提取了现实的有效自旋模型，并发现当配体元素较重时，SOC效应仅在特定填充情况下表现为各向异性交换和单离子各向异性。 显示英文摘要

摘要： Motivated by the recent wealth of exotic magnetic phases emerging in two-dimensional frustrated lattices, we investigate the origin of possible magnetism in the monolayer family of triangular lattice materials $MX_2$ ($M$={V, Mn, Ni}, $X$={Cl, Br, I}). We first show that consideration of general properties such as filling and hybridization enables to formulate trends for the most relevant magnetic interaction parameters. In particular, we observe that the effects of spin-orbit coupling (SOC) can be effectively tuned through the ligand elements as the considered 3$d$ transition metal ions do not strongly contribute to the anisotropic component of the inter-site exchange interaction. Consequently, we find that the corresponding SOC matrix-elements differ significantly from the atomic limit. In a next step and by using two complementary approaches based on first principles, we extract realistic effective spin models and find that in the case of heavy ligand elements, SOC effects manifest in anisotropic exchange and single-ion anisotropy only for specific fillings.