Hydrothermal synthesis, crystal structure, and magnetic properties of FeVO4-II

FeVO4-II, a metastable phase so far produced under high pressures, has been synthesized by a hydrothermal method from a solution of VOCl2 and FeCl3. FeVO4-II crystallizes in the orthorhombic system: Cmcm, a = 5.6284(7) Angstrom, b = 8.2724(7) Angstrom, c = 6.1118(6) Angstrom, with Z = 4, The single-crystal structure refinements verified a CrVO4-type structure and converged to R/R(W), = 0.035/0.029 for 324 reflections with I > 3 sigma(I), The structure consists of FeO6 octahedra and VO4 tetrahedra where edge-sharing FeO6 octahedra form isolated FeO4 chains running parallel to the c axis and the chains are joined by VO4 tetrahedra, The temperature dependence of magnetic susceptibility featured by a broad maximum around 52 K suggests the predominance of one-dimensional antiferromagnetic interactions in the FeO4 chains, A three-dimensional antiferromagnetic order is attained somewhere below 40 K yielding a hyperfine field of 483 KOe at 4.2 K observed in the Mossbauer spectrum. (C) 1996 Academic Press, Inc.