ChemInform Abstract: A New Ferric Orthoarsenate Hydrate: Structure and Magnetic Ordering of FeAsO4×3/4H2O.
Abstract
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ChemInform Abstract
The title compound is obtained from the hydrothermal reaction between Fe2O3 and 4 M H3AsO4 (700-800 °C, 3 kbar, 12 h). FeAsO4×0. 75 H2O crystallizes in the triclinic space group P1 with Z = 4 (powder and single crystal XRD). The structure contains novel tetrameric units of iron octahedra, Fe4O16(OH2)2, which are interconnected by AsO4 tetrahedra to form a network with open channels containing the water molecules. Moessbauer data obtained over the temp. range 298-4.2 K reveal a transition to a three-dimensional magnetically ordered state at ≅47.5 K. The Zeeman-split spectra show the presence of two inequivalent iron sites. Magnetic susceptibility measurements indicate antiferromagnetic ordering below ≅49 K. The Curie-Weiss fit in the paramagnetic region yields a magnetic moment of 5.68 μB.
