反萤石层对Eu基1111化合物EuTAsF（T = Zn，Mn，Fe）磁有序性的影响
Effect of antifluorite layer on the magnetic order in Eu-based 1111 compounds, EuTAsF (T = Zn, Mn, and Fe)
摘要：
1111化合物与交替序列的萤石和反萤石层作为结构主机的庞大家庭的铁基超导体。在这里，我们使用中子粉末衍射和密度泛函理论（DFT）的能带结构计算来研究的[EuF]+萤石层中的Eu 2+的磁性顺序取决于[TA]-反萤石层的性质，可以是非磁性半导体（T = Zn），磁性半导体（T = Mn），或磁性金属（T = Fe）。反铁磁转变TN ~ 2.4 - 3 K由于有序的Eu 2+磁矩被证实在所有三个EuTASF化合物。在EuTAsF（T = Zn和Mn）中，观察到与ab面内的磁矩相称的k1 =（1/2 1/2 0）条序图案，而在EuFeAsF中，观察到与k =（0 0.961（1）1/2）不相称的条序图案，并表示限制在bc面内的Eu 2+磁矩的摆线。此外，在EuMnAsF的Mn 2+亚晶格具有强大的G型反铁磁秩序，至少持续到室温，沿c方向的磁矩。虽然DFT计算表明条纹反铁磁序的Fe亚晶格的EuFeAsF的基态，中子衍射显示没有证据的长程磁序与Fe。我们表明，相邻的[EuF]+层之间的令人沮丧的面间相互作用J3是可比的面内J1-J2相互作用已经在半导体萤石层[TA]-（T = Zn和Mn）的情况下，并成为占主导地位的金属[FeAs]-的情况下。后者，随着轻微的正交畸变，提出了在EuFeAsF中观察到的无公度磁结构的起源。
英文摘要：
The 1111 compounds with an alternating sequence of fluorite and antifluorite layers serve as structural hosts for the vast family of Fe-based superconductors. Here, we use neutron powder diffraction and density-functional-theory (DFT) band-structure calculations to study magnetic order of Eu2+ in the [EuF]+ fluorite layers depending on the nature of the [TAs]- antifluorite layer that can be non-magnetic semiconducting (T = Zn), magnetic semiconducting (T = Mn), or magnetic metallic (T = Fe). Antiferromagnetic transitions at TN ~ 2.4 - 3 K due to an ordering of the Eu2+ magnetic moments were confirmed in all three EuTAsF compounds. Whereas in EuTAsF (T = Zn and Mn), the commensurate k1 = (1/2 1/2 0) stripe order pattern with magnetic moments within the ab-plane is observed, the order in EuFeAsF is incommensurate with k = (0 0.961(1) 1/2) and represents a cycloid of Eu2+ magnetic moments confined within the bc-plane. Additionally, the Mn2+ sublattice in EuMnAsF features a robust G-type antiferromagnetic order that persists at least up to room temperature, with magnetic moments along the c-direction. Although DFT calculations suggest stripe antiferromagnetic order in the Fe-sublattice of EuFeAsF as the ground state, neutron diffraction reveals no evidence of long-range magnetic order associated with Fe. We show that the frustrating interplane interaction J3 between the adjacent [EuF]+ layers is comparable with in-plane J1-J2 interactions already in the case of semiconducting fluorite layers [TAs]- (T = Zn and Mn) and becomes dominant in the case of the metallic [FeAs]- ones. The latter, along with a slight orthorhombic distortion, is proposed to be the origin of the incommensurate magnetic structure observed in EuFeAsF.
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