CRYSTAL-STRUCTURES AND MOSSBAUER-SPECTRA OF LAFE1-XMNXO3 AND LAFE1-XCOXO3 (X=0 TO 0.9)

The crystal structures and Mossbauer spectra of various mixed oxides L aFe1-xMnxO3 and LaFe1-xCoxO3 (x = 0 to 0.9) are determined and measure d at room temperature. The results indicate that the crystal structure of both the La-Fe-Mn-O and the La-Fe-Co-O systems vary with the relat ive content of manganese and cobalt in the compounds. Mossbauer parame ters of the Fe-57 nucleus in these compounds, such as isomer shift, el ectric quadrupole splitting, linewidth, and internal magnetic field, a re obtained from the experimental spectra. Various possible substituti ons of Mn and Co ions for Fe ions in the lattice and the effect of the Mn and Co ions on the Mossbauer spectra of the Fe-57 nucleus in these compounds are discussed. Both manganese and cobalt ions in these comp ounds are mainly in a low spin state. The change in the crystal struct ure is in accordance with the change in the magnetic behaviour of thes e compounds.