A Mössbauer investigation of Sr1−xLaxFe12O19 (0≤x≤1) M-type hexaferrites

Sr1−xLaxFe12O19 hexaferrite powders prepared using a standard ceramic process were investigated by Mössbauer spectrometry, thus allowing investigating the influence of the Sr2+/La3+ substitution on the five Fe sublattices in the whole range of composition. Very satisfactory fittings are obtained accounting for the Fe2+/Fe3+ charge compensation mechanism at the 2a site due to the replacement of Sr2+ by La3+. The evolutions of the hyperfine parameters (hyperfine field, isomer shift and quadrupolar shift) of the contributions related to the five iron sites are continuous. They are interpreted in relation with the Sr2+/La3+ substitution. The results show that the 12k, 4f2 and 2b sites are the most affected by the substitution, in agreement with both the evolution of the lattice constants and the fact that these three sites have Sr sites in their close vicinity.