Synthesis, crystal structure, and magnetism of Fe sub 4 (OH) sub 3 (PO sub 4 ) sub 3 and V sub 4 O(OH) sub 2 (PO sub 4 ) sub 3 : Chains of M sub 2 O sub 9 dimers connected by hydroxyl groups
- E.I. Du Pont de Nemours and Co., Wilmington, DE (USA)
- Northeastern Univ., Boston, MA (USA)
The new compounds Fe{sub 4}(OH){sub 3}(PO{sub 4}){sub 3} and V{sub 4}O(OH){sub 2}(PO{sub 4}){sub 3} are prepared hydrothermally by reaction of Fe{sub 2}O{sub 3} and V{sub 2}O{sub 3} with aqueous H{sub 3}PO{sub 4} solutions. X-ray powder diffraction shows that the two compounds have the same monoclinic structure. Fe{sub 4}(OH){sub 3}(PO{sub 4}){sub 3} crystallizes with unit cell parameters a = 19.555(2), b = 7.376(1), c = 7.429(1) {angstrom}, and {beta} = 102.26(1){degree} in the space group C2/c with Z = 4. Dimers of face-sharing (nonequivalent) FeO{sub 6} octahedra are interconnected by OH groups to form a double-chain of dimers extended along the c axis. Double chains are linked to one another by PO{sub 4} tetrahedra that share corners with the octahedra. The Moessbauer spectrum of Fe{sub 4}(OH){sub 3}(PO{sub 4}){sub 3} at 293 K exhibits two narrow width quadrupole doublets of equal intensity, with nearly identical isomer shifts and different quadrupole splittings: {delta}{sub 1} = 0.407 mm/sec, {delta}{sub 2} = 0.403 mm/sec, {Delta}E{sub 1} = 0.657 mm/sec, {Delta}E{sub 2} = 0.294 mm/sec. Low-temperature spectra indicate magnetic hyperfine splitting and three-dimensional magnetic order among the dimers at 86.7 {plus minus} 0.2 K. Below the ordering temperature, the spectrum consists of two equal intensity sextets with saturation hyperfine fields (4.2 K) of 52.9 and 49.1 T, respectively. The temperature dependence of the magnetic susceptibility confirms that ordering occurs at 87 {plus minus} 0.5 K with an abrupt rise to a high-moment ferromagnetic state. Above the ordering temperature, the susceptibility data exhibits a broad maximum at about 125 K characteristic of antiferromagnetically coupled dimers. The moment vs. temperature behavior of V{sub 4}O(OH){sub 2}(PO{sub 4}){sub 3} also shows antiferromagnetic exchange that is likely pairwise in nature.
- OSTI ID:
- 7247478
- Journal Information:
- Journal of Solid State Chemistry; (USA), Vol. 82:2; ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
IRON HYDROXIDES
CRYSTAL STRUCTURE
MAGNETISM
SYNTHESIS
PHOSPHIDES
VANADIUM HYDROXIDES
DATA ANALYSIS
DIMERS
EXPERIMENTAL DATA
MEASURING INSTRUMENTS
MEASURING METHODS
DATA
HYDROGEN COMPOUNDS
HYDROXIDES
INFORMATION
IRON COMPOUNDS
NUMERICAL DATA
OXYGEN COMPOUNDS
PHOSPHORUS COMPOUNDS
PNICTIDES
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
360000* - Materials
360102 - Metals & Alloys- Structure & Phase Studies
400000 - Chemistry