Emission Mössbauer studies of ⁵⁷Co²⁺ and ¹¹⁹Sb⁵⁺ adsorbed on γ-Fe₂O₃ and NiFe₂O₄ surfaces

Summary

Surface chemical states of ⁵⁷Co²⁺ and ¹¹⁹Sb⁵⁺ ions adsorbed on γ-Fe₂O₃ and NiFe₂O₄ were studied in the presence of the aqueous phase using the magnetic interaction between the substrates and ⁵⁷Fe²⁺ or ¹¹⁹Sn⁴⁺ arising from the adsorbed species. Two chemical forms were observed for the ⁵⁷Co²⁺ adsorbed on γ-Fe₂O₃; one giving a peak in the high-field region and another giving a broad distribution in the lower fields, which were attributed to ⁵⁷Co²⁺ at surface B sites of the spinel structure of γ-Fe₂O₃ and ⁵⁷Co²⁺ species weakly bonded to the substrate, respectively. In case of the NiFe₂O₄ substrate, the latter species was dominant and was converted to the former by heating. Most of the ¹¹⁹Sb⁵⁺ ions adsorbed on the γ-Fe₂O₃ and NiFe₂O₄ particles were found to have a certain magnetic interaction with the magnetically ordered ions of the substrates.