Sheath Bradley C, Savvin Stanislav, Clarke Simon J
Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR, United Kingdom.
Institut Laue-Langevin, 71 Avenue des Martyrs CS 20156, Grenoble 38042, France.
Inorg Chem. 2024 Dec 9;63(49):23267-23275. doi: 10.1021/acs.inorgchem.4c03770. Epub 2024 Nov 25.
BaFeSbS and BaFeBiS are two isostructural quaternary sulfides that crystallize in the space group with four formula units per unit cell. BaFeSbS has lattice parameters = 12.08609(3) Å, = 8.83426(2) Å, and = 8.89114(2) Å, and BaFeBiS has = 12.09610(3) Å, = 8.89281(2) Å, and = 8.82437(2) Å at room temperature. They comprise infinite [FeMS] (M = Sb, Bi) chains, where Fe is present in FeS tetrahedra and M ions reside in edge-sharing MS distorted octahedra, each of which shares an edge with an FeS tetrahedron. Powder neutron diffraction measurements confirm the presence of long-range antiferromagnetic order of the Fe moments in both materials, where Fe-S···S-Fe super-superexchange interactions which act along the direction of the [FeMS] (M = Sb, Bi) chains are the driving force for this antiferromagnetic order. The magnetic Bragg reflections reside on a -vector with = (1/2 0 1/2), and the relative orientations of the moments are similar in the two cases One significant difference is that the moments are aligned along the crystallographic -axis in BaFeSbS, whereas in BaFeBiS they lie along the longer crystallographic -axis, reflecting the weak directional preference of the Fe moments. Furthermore, an additional incommensurately modulated ordering of the Fe moments is suggested for BaFeSbS (but not BaFeBiS) by the appearance of small additional magnetic Bragg peaks in the neutron diffraction data, which may be a consequence of greater magnetic frustration in BaFeSbS.
BaFeSbS和BaFeBiS是两种同构的四元硫化物，它们在空间群中结晶，每个晶胞包含四个化学式单元。BaFeSbS的晶格参数为(a = 12.08609(3) Å)，(b = 8.83426(2) Å)，(c = 8.89114(2) Å)，室温下BaFeBiS的晶格参数为(a = 12.09610(3) Å)，(b = 8.89281(2) Å)，(c = 8.82437(2) Å)。它们由无限的[FeMS]（M = Sb，Bi）链组成，其中Fe存在于FeS四面体中，M离子位于共边的MS扭曲八面体中，每个八面体与一个FeS四面体共享一条边。粉末中子衍射测量证实了这两种材料中Fe磁矩的长程反铁磁序，其中沿着[FeMS]（M = Sb，Bi）链方向起作用的Fe-S···S-Fe超超交换相互作用是这种反铁磁序的驱动力。磁布拉格反射位于(h)矢量为((1/2 0 1/2))的位置，两种情况下磁矩的相对取向相似。一个显著的区别是，在BaFeSbS中磁矩沿结晶学(c)轴排列，而在BaFeBiS中它们沿较长的结晶学(b)轴排列，这反映了Fe磁矩的弱方向偏好。此外，中子衍射数据中出现的小的附加磁布拉格峰表明BaFeSbS（而非BaFeBiS）存在Fe磁矩的额外非相称调制有序，这可能是BaFeSbS中更大的磁阻挫的结果。
