非化学计量Sr $_{1-y}$ Mn $_{1-z}$ Sb $_{2}$（y，z~ $<$ 0.1）的准二维磁性和狄拉克半金属行为的起源
Quasi-2D magnetism and origin of the Dirac semimetallic behavior in nonstoichiometric Sr$_{1-y}$Mn$_{1-z}$Sb$_{2}$ (y, z~$<$0.1)
摘要：
非化学计量比的Sr $_{1-y}$ Mn $_{1-z}$ Sb $_{2}$（y，z~ $<$ 0.1）表现出磁有序和与狄拉克或外尔费米子相关的非平凡半金属行为的共存。在这里，我们报告非弹性中子散射分析的自旋动力学和密度泛函理论研究的电子性质的Sr $_{1-y}$ Mn $_{1-z}$ Sb $_{2}$。在5 K时，我们观察到一个相对较大的自旋激发能隙$\approx$ 8.5 meV，层间磁交换常数仅为主要层内磁相互作用的2.8%，这为Sr $_{1-y}$ Mn $_{1-z}$ Sb $_{2}$表现出准二维磁性提供了证据.利用密度泛函理论，我们发现在铁磁有序存在的情况下，磁有序对费米能级附近沿Y-S方向的电子能带结构和狄拉克色散有很强的影响.我们的研究揭示了Sr $_{1-y}$ Mn $_{1-z}$ Sb $_{2}$中磁有序、磁跃迁和电子性质之间的新的相互作用，为通过磁性控制三元化合物的相对论能带结构开辟了新的途径.
英文摘要：
Nonstoichiometric Sr$_{1-y}$Mn$_{1-z}$Sb$_{2}$ (y, z~$<$0.1) is known to exhibit a coexistence of magnetic order and the nontrivial semimetallic behavior related to Dirac or Weyl fermions. Here, we report inelastic neutron scattering analyses of the spin dynamics and density functional theory studies on the electronic properties of Sr$_{1-y}$Mn$_{1-z}$Sb$_{2}$. We observe a relatively large spin excitation gap $\approx$ 8.5 meV at 5 K, and the interlayer magnetic exchange constant only 2.8 \% of the dominant intralayer magnetic interaction, providing evidence that Sr$_{1-y}$Mn$_{1-z}$Sb$_{2}$ exhibits a quasi-2D magnetism. Using density functional theory, we find a strong influence of magnetic orders on the electronic band structure and the Dirac dispersions near the Fermi level along the Y-S direction in the presence of a ferromagnetic ordering. Our study unveils novel interplay between the magnetic order, magnetic transition, and electronic property in Sr$_{1-y}$Mn$_{1-z}$Sb$_{2}$, and opens new pathways to control the relativistic band structure through magnetism in ternary compounds.
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