Investigation of (R1−xR′x)2(Fe,Co)17 powders by Mössbauer spectrometry

We investigated (R1−xR′x)2Fe17 and (R1−xR′x)2Fe16Co powders by 57Fe Mössbauer spectrometry at 295 K where R and R′ are Y, Nd, Sm, Gd. The spectra of the (R1−xR′x)2Fe17 compounds have been fitted with seven sextets: 18f12, 18f6, 18h12, 18h6, 9d6, 9d3 and 6c. The isomer shifts of the different Fe sites are in agreement with the Wigner-Seitz cell volumes. They do not depend on the nature of the rare earth. The hyperfine fields are consistent with the evolution of the Curie temperature. To account for substitution effects due to the partial replacement of Fe by Co, the Mössbauer spectra of the (R1−xR′x)2Fe16Co samples have been fitted with four sextets corresponding to the 18f, 18h, 9d, and 6c Fe sites, by considering the site occupancy of the Co atoms in the lattice. The evolution of the hyperfine field with the rare-earth concentration is discussed and interpreted in relation with the magnetic coupling between rare-earth and Fe magnetic sublattices, in agreement with previous magnetic measurements.