XANES study and rietveld refinement for the nanometer sized polycrystalline ferrite, AFe12O19 (A=Sr, Ba)

X-ray absorption near edge structure and Rietveld refinement were performed in order to investigate the structural feature and the magnetic origin of magnetoplumbite type nanometer sized (≅ 50nm) ferrite. The increase of covalency of the presence of higher oxidation state (Fe4+) could not be observed in XANES. According to the Rietveld refinement, the Sr-ferrite has shorter bond distances because of the difference in ionic size. The larger magnetic value (Hc =6500 Oe) of Sr-ferrite might be due to the reduced FeO bond distance which leads to a stronger ferromagnetic coupling between the Fe3+ ions in the lattice.