Structure and magnetism in hexagonal tungsten bronze metal oxides AM1/3W8/3O9 (A–K, Rb, Cs; M–Cr, Fe)

•The structural properties of hexagonal tungsten bronzes have been investigated in detail.•Materials were phase pure AM1/3W8/3O9 (A–K+, Rb+, Cs+; M–Cr3+, Fe3+).•Ferroelectricity has been observed in this class of materials.•We observe a weak magnetic interaction, of antiferromagnetic nature.

The structure and magnetic properties of hexagonal tungsten bronzes AM1/3W8/3O9 (A–K+, Rb+, Cs+; M− Cr3+, Fe3+) have been investigated. Pure ceramic samples were synthesized by solid-state reaction. The samples have been studied by X-ray powder diffraction in combination with magnetic measurements. The compounds crystallize in hexagonal space group P63/mcm. The substitution of magnetic ions into the WO6 octahedra yields dilute antiferromagnetic Cr3+-O2−-Cr3+ (or Fe3+-O2−-Fe3+) superexchange interaction causing the appearance of short-range magnetic order at low temperatures. The antiferromagnetic character of the interaction is supported by negative values of the derived Curie–Weiss temperatures, θCW. The magnitude of θCW is found to decrease with increasing ionic radius of the A cation.

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