Magnetic and electrical properties of Eu2VO4

Eu2VO4 with the K2NiF4-type structure was prepared by heating Eu2O3, V2O5, and V metal at 1473 K in an evacuated silica ampoule. Rietveld refinement of the powder X-ray diffraction (XRD) data confirmed the presence of layers of corner-shared VO6 octahedra with V–O bond distances of 1.928(1) Å (× 4) and 2.04(2) Å (× 2) perpendicular to the tetragonal c axis. X-ray absorption near-edge spectroscopy (XANES) indicated that the Eu is mixed-valent [Eu(II)/Eu(III)], while vanadium exists exclusively in the trivalent state. These valence assignments were supported by the results of temperature-dependent magnetic susceptibility and Mössbauer spectroscopy data. Variable temperature electrical resistivity measurements indicated that the sample was insulating (ρRT ≈ 104 Ω-cm). The compound undergoes a charge-ordering transition associated with the Eu sublattice at 445 K, as evidenced by Mössbauer spectroscopy, electrical resistivity, and in situ high temperature X-ray diffraction studies.