IN-SITU EMISSION MOSSBAUER STUDIES ON CARRIER-FREE CO-57(2-119(5+) IONS AT INTERFACES BETWEEN SPINEL-TYPE OXIDES AND AQUEOUS-SOLUTIONS() AND SB)

Surface chemical states of carrier-free Co-57(2+) and Sb-119(5+) ions adsorbed on gamma-Fe2O3 and NiFe2O4 were studied in the presence of th e aqueous phase using the magnetic interaction between the substrates and Fe-57(3+) Or Sn-119(4+) arising from the adsorbed species. Two che mical forms were observed for the Co-57(2+) adsorbed on gamma-Fe2O3, o ne giving a peak in the high-field region and another giving a broad d istribution in the low field. They were attributed to Co-57(2+) at sur face B sites of the spinel structure of gamma-Fe2O3 and Co-57(2+) spec ies weakly bonded to the substrate, respectively. In case of NiFe2O4, the latter species was dominant, being converted to the former by heat ing. Most of the Sb-119(5+) ions adsorbed on the gamma-Fe2O3 and NiFe2 O4 particles were found to have more or less magnetic interaction with the magnetically ordered ions of the substrates.