Chemical state of cobalt doped in and adsorbed on α-(Fe1-xCr x )2O3 by emission Mössbauer spectroscopy
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Mössbauer parameters (internal magnetic field, quadrupole splitting and isomer shift) of both α-(Fe1-xCr x )2O3 (x=0, 0.2 and ≈1.0) doped and undoped with57Co are in good agreement at room temperature and 77 K, except internal magnetic fields of both α-Cr2O3 doped with57Co and enriched57Fe. It is thus concluded that57Fe produced from57Co occupies the octahedral sites as Fe3+ with small distortion from cubic symmetry. Different internal magnetic field of doped α-Cr2O3 may be explained by the difference of canting of the spin against the  axis.
By adding zinc ions, the adsorption of Co2+ ions on α-Fe2O3 particles in aqueous solution is decreased considerably in the pH range of 6.5–9.5 at 303 K, but the internal magnetic field of57Co adsorbed on α-Fe2O3 does not change, although the internal magnetic fields of both samples with and without zinc ions are smaller than that of bulk α-Fe2O3 doped with57Co. This suggests that densities of57Co ions on the surface of α-Fe2O3 may be decreased by the addition of zinc ions and57Co ions adsorbed on α-Fe2O3 are weakly bound on the substrate.
KeywordsSpectroscopy Zinc Magnetic Field Thin Film Aqueous Solution
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