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

Abstract

Three mixed-valence barium iron fluorides, Ba₇Fe₇F₃₄, Ba₂Fe₂F₉, and BaFe₂F₇, were prepared through hydrothermal redox reactions. The characteristic structures of these compounds feature diverse distributions of Fe^IIF₆ octahedra and Fe^IIIF₆ groups. Ba₇Fe₇F₃₄ contained one-dimensional infinite _∞[Fe^IIFe^III₆F₃₄]^14- double chains, comprising cis corner-sharing octahedra along the b direction; Ba₂Fe₂F₉ contained one-dimensional _∞[Fe₂F₉]^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 BaFe₂F₇ revealed three-dimensional (3D) frameworks that consist of isolated edge-sharing dinuclear Fe^II₂F₁₀ units linked via corners by Fe^IIIF₆ octahedra. Magnetization and Mössbauer spectroscopy measurements revealed that Ba₇Fe₇F₃₄ exhibits an antiferromagnetic phase transition at ∼11 K, where ferrimagnetic _∞[Fe^IIFe^III₆F₃₄]^14- double chains are arranged in a paralleling manner, while Ba₂Fe₂F₉ shows canted antiferromagnetic ordering at ∼32.5 K, leading to noncollinear spin ordering.