Investigation of Charge-Ordered Barium Iron Fluorides with One-Dimensional Structural Diversity and Complex Magnetic Interactions.

Three mixed-valence barium iron fluorides, Ba 7 Fe 7 F 34 , Ba 2 Fe 2 F 9 , and BaFe 2 F 7 , were prepared through hydrothermal redox reactions. The characteristic structures of these compounds feature diverse distributions of Fe II F 6 octahedra and Fe III F 6 groups. Ba 7 Fe 7 F 34 contained one-dimensional infinite ∞ [Fe II Fe III 6 F 34 ] 14- double chains, comprising cis corner-sharing octahedra along the b direction; Ba 2 Fe 2 F 9 contained one-dimensional ∞ [Fe 2 F 9 ] 4- double chains, consisting of cis corner-sharing octahedra along the chain ( a -axis direction) and trans corner-sharing octahedra vertical to the chain, while BaFe 2 F 7 revealed three-dimensional (3D) frameworks that consist of isolated edge-sharing dinuclear Fe II 2 F 10 units linked via corners by Fe III F 6 octahedra. Magnetization and Mössbauer spectroscopy measurements revealed that Ba 7 Fe 7 F 34 exhibits an antiferromagnetic phase transition at ∼11 K, where ferrimagnetic ∞ [Fe II Fe III 6 F 34 ] 14- double chains are arranged in a paralleling manner, while Ba 2 Fe 2 F 9 shows canted antiferromagnetic ordering at ∼32.5 K, leading to noncollinear spin ordering.