Magnetic Properties of Fresnoite-Type Vanadium Oxides: A2V3O8 (A = K, Rb, NH4)

Methods for synthesizing large amounts of polycrystalline A2 V3O8 (A = K, Rb, and NH4) are introduced, Crystals of Rb2V3O8 have been grown in a RbBr flux and the crystal structure has been confirmed by single crystal X-ray diffraction. Magnetic susceptibility data of these fresnoite-type vanadium oxides are presented. All three compounds exhibit short-range magnetic correlations below 10 K. The susceptibility data are analyzed based on a two-dimensional square-planar model. The interactions are antiferromagnetic and the magnitude of the exchange (-J/k) decreases in the order K2V3O8, Rb2V3O8, and (NH4)2V3O8.