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Magnetic and Mossbauer effect studies have been reported for new UFe10Si2, UCo10Si2 and UFe10Mo2 compounds crystallizing with tetragonal structure of the ThMn12-type. The magnetization measurements have been performed for the magnetic field preoriented sample of UFe10Si2 and bulk sample of UCo10Si2, in high fields up to 140 kOe. The 57Fe Mossbauer spectra for UFe10Si2 and UFe10Mo2 have been recorded below the corresponding Curie temperatures.

The 57 Fe Mossbauer resonance has been applied to study polyacetylene films doped chemically and electrochemically to different doping levels. Both methods lead to the insertion of a high spin Fe III complex with Mossbauer parameters characteristic of FeCl − 4 . Degradation of [CH(FeCl 4 ) y ] x in air leads to gradual transformation of Fe III into a high spin Fe II .

The hyperfine interaction parameters at the 161Dy and 57Fe nuclei in Dy2Fe17−yAly compounds (0 ⩽ y ⩽ 8) have been determined from the Mossbauer effect measurements at 4.2 K. The excess of the hyperfine magnetic field at the 161Dy nuclei is discussed according to the 5d electron transfer model.

Very active catalysts can be prepared from FeCl3-GIC precursors through a two-step reduction and washing with HCl. Mossbauer spectrometry during the first (H2) reduction step indicates that Fe0 in the form of α-Fe is obtained together with two non-equivalent FeII sites. This α-Fe is catalytically inactive and can be readily removed from the system treatment with HCl. The second reduction with potassium vapour transforms the remaining FeII into catalytically active Fe0 which is strongly resistant to the HCl treatment.

The compounds Dy 2 Fe 17− y Co y (O⩽ y ⩽17) have been investigated using the Mossbauer resonances at the 161 Dy and 57 Fe nuclei (at 4.2 K). The changes of the hyperfine interaction parameters have been determined as a function of the Co content. The dependence of the hyperfine field at the 57 Fe nuclei on y is quite different from that for the 161 Dy nuclei. The 5d electron model is proposed to explain this behaviour.

The hyperfine interaction parameters at the 161Dy and 57Fe nuclei in Dy2−yYyFe17 compounds (0⩽y⩽2) have been determined from the Mossbauer effect measurements at 4.2 K. The dysprosium atoms are substituted by the yttrium atoms across the series and then the 5d electrons of Dy are replaced by the 4d electrons of Y. The hyperfine interaction parameters for both nuclei remain constant versus Y content. The full equivalency between 5d and 4d electrons has been deduced. The excess of the hyperfine magnetic field at the 161Dy nuclei and the reduction of the magnetic hyperfine field at the 57Fe nuclei can be explained as a result of the presence of the magnetically polarized 5d (or 4d) electrons in these compounds.