MOSSBAUER INVESTIGATION OF ALUMINUM SUBSTITUTED BARIUM HEXAFERRITE IN THE PARAMAGNETIC STATE

Fe-57-Mossbauer measurements have been performed on aluminium substituted M-type barium hexaferrites of composition BaFe12-xAlxO19 (0 less than or equal to x less than or equal to 9.6) above their Curie temperatures. The quadrupole splitting values for Fe-57 nuclei in the five iron sublattices of the crystalline structure as a function of x have been determined up to the highest x value. For the non-substituted BaFe12O19 ferrite, the comparison of the obtained data with that measured below the Curie temperature, allowed a determination of the angle between the direction of the magnetization and the electric field gradient axis at the Fe-57 nuclei in the octahedrally coordinated lattice sites. For x less than or equal to 6 a high rate of substitution of Fe3+ by Al3+ ions occurs in the k lattice sites responsible for the magnetic interactions between the spinel and the hexagonal structural blocks.