title: Ba4KFe3O9: a novel ferrite containing discrete 6-membered rings of corner-sharing FeO4 tetrahedra.
abstract: Single crystals of a new iron-containing oxide, Ba(4)KFe(3)O(9), were grown from a hydroxide melt, and the crystal structure was determined by single-crystal X-ray diffraction. This ferrite represents the first complex oxide containing isolated 6-membered rings of corner-sharing FeO(4) tetrahedra. Mössbauer measurements are indicative of two tetrahedral high-spin Fe(3+) coordination environments. The observed magnetic moment (~3.9 μ(B)) at 400 K is significantly lower than the calculated spin-only (~5.2 μ(B)) value, indicating the presence of strong antiferromagnetic interactions in the oxide. Our density functional theory calculations confirm the strong antiferromagnetic coupling between adjacent Fe(3+) sites within each 6-membered ring and estimate the nearest-neighbor spin-exchange integral as ~200 K; next-nearest-neighbor interactions are shown to be negligible. The lower than expected effective magnetic moment for Ba(4)KFe(3)O(9) calculated from χT data is explained as resulting from the occupation of lower-lying magnetic states in which more spins are paired. X-band (9.5 GHz) electron paramagnetic resonance (EPR) spectra of a powder sample consist of a single line at g ~ 2.01 that is characteristic of Fe(3+) ions in a tetrahedral environment, thus confirming the Mössbauer results. Further analysis of the EPR line shape reveals the presence of two types of Fe(6) magnetic species with an intensity ratio of ~1:9. Both species have Lorentzian line shapes and indistinguishable g factors but differ in their peak-to-peak line widths (δB(pp)). The line-width ratio δB(pp)(major)/δB(pp)(minor) ~ 3.6 correlates well with the ratio of the Weiss constants, θ(minor)/θ(major) ~ 4.
authors: Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA.
authors: Qingbiao
authors: Q
authors: Zhao
authors: Saritha
authors: S
authors: Nellutla
authors: Won-Joon
authors: WJ
authors: Son
authors: Shae A
authors: SA
authors: Vaughn
authors: Longfei
authors: L
authors: Ye
authors: Mark D
authors: MD
authors: Smith
authors: Vincent
authors: V
authors: Caignaert
authors: Michael
authors: M
authors: Lufaso
authors: Thomas M
authors: TM
authors: Pekarek
authors: Alex I
authors: AI
authors: Smirnov
authors: Myung-Hwan
authors: MH
authors: Whangbo
authors: Hans-Conrad
authors: HC
authors: zur Loye
mesh_terms: D001896:Boron Compounds / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D005290:Ferric Compounds / Q000737:chemistry*; D006358:Hot Temperature; D058085:Iron Compounds / Q000737:chemistry*; D060328:Magnetic Phenomena; D008958:Models, Molecular; D008968:Molecular Conformation; D010087:Oxides / Q000737:chemistry*; D011789:Quantum Theory; D015204:Spectroscopy, Mossbauer
chemical_list: D001896:Boron Compounds; D005290:Ferric Compounds; D058085:Iron Compounds; D010087:Oxides; C001215:ferrite