Effect of the divalent iron on the Moessbauer parameters of Cosub(x)2+Fesub(1-x)2+Fe23+O4 ferrites

Moessbauer effect measurements have been carried out for the composition Cosub(x)2+Fesub(1-x)2+Fe23+O4 with x = 0, 0.2 and 1. The stoichiometric compound CoFe2O4 gives a broad six lines spectrum. On the substitution of Co2+ by Fe2+, two superimposed Zeeman patterns appeared, the new lines are attributed to the presence of the divalent iron in the high spin state. For the compound with x = 0, two samples of Fe3O4 (high purity commercial and natural magnetites) are also measured and show distinct different spectra. Moessbauer parameters for the different samples are calculated and the significance of the various spectra in relation to the structure of these mixed oxides is discussed. (orig.)