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Synthesis, Structure, and a Mössbauer and Magnetic Study of Ba₄Fe₂I₅S₄
Inorganic Chemistry
  • Danielle L. Gray
  • Gary J. Long, Missouri University of Science and Technology
  • Fernande Grandjean, Missouri University of Science and Technology
  • Raphäel P. Hermann
  • James A. Ibers

The compound Ba4Fe2I5S4 has been prepared at 1223-1123 K by the "U-assisted" reaction of FeS, BaS, S, and U with BaI2 as a flux. A more rational synthesis was also found; however, the presence of U appears to be essential for the formation of single crystals suitable for X-ray diffraction studies. Ba4Fe 2I5S4 crystallizes in a new structure type with two formula units in space group I4/m of the tetragonal system. The structure consists of a Ba-I network penetrated by ∞ 1[Fe 2S4] chains. Each Fe atom, which is located on a site with 4 symmetry, is tetrahedrally coordinated to four S atoms. The FeS4 tetrahedra edge-share to form linear ∞ 1[Fe 2S4] chains in the [001] direction. The Fe-Fe interatomic distance in these chains is 2.5630(4) Å, only about 3% longer than the shortest Fe-Fe distance in α-Fe metal. Charge balance dictates that the average formal oxidation state of Fe in these chains is +2.5. The Mössbauer spectra obtained at 85 and 270 K comprise a single quadrupole doublet that has hyperfine parameters consistent with an average Fe oxidation state of +2.5. The Mössbauer spectrum obtained at 4.2 K consists of a single magnetic sextet with a small hyperfine field of -15.5 T. This spectrum is also consistent with rapid electron derealization and an average Fe oxidation state of +2.5. The molar magnetic susceptibility of Ba4-Fe2I 5S4, obtained between 3.4 and 300 K, qualitatively indicates the presence of weak pseudo-one-dimensional ferromagnetic exchange within a linear chain above 100 K and weak three-dimensional ordering between the chains at lower temperatures.

Document Type
Article - Journal
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File Type
© 2008 American Chemical Society (ACS), All rights reserved.
Publication Date
Publication Date
01 Jan 2008
Citation Information
Danielle L. Gray, Gary J. Long, Fernande Grandjean, Raphäel P. Hermann, et al.. "Synthesis, Structure, and a Mössbauer and Magnetic Study of Ba₄Fe₂I₅S₄" Inorganic Chemistry Vol. 47 Iss. 1 (2008) p. 94 - 100 ISSN: 0020-1669
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