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( R 1 − x R ′ x ) F e 17 − y C o y powders were prepared by induction melting. Nitrogen (2.9 ± 0.1 atoms per formula unit) was inserted under a static nitrogen gas atmosphere. The nitrided powders have been investigated by 57 Fe Mossbauer spectrometry and X-ray diffraction. The analyses show that the samples are composed of two phases: the nitrided ( R 1 − x R ′ x ) F e 17 − y C o y N z phase and α-Fe. The variations of the Mossbauer hyperfine parameters of the nitrided phase are explained both by the lattice expansion and by the presence of nitrogen. The observed variations do not indicate an influence of the rare-earth on the isomer shift. Nitrogenation increases the hyperfine field at the Fe sites in agreement with the enhancement of the Curie temperature.

We investigated (R 1− x R′ x ) 2 Fe 17 and (R 1− x R′ x ) 2 Fe 16 Co powders by 57 Fe Mossbauer spectrometry at 295 K where R and R′ are Y, Nd, Sm, Gd. The spectra of the (R 1− x R′ x ) 2 Fe 17 compounds have been fitted with seven sextets: 18f 12 , 18f 6 , 18h 12 , 18h 6 , 9d 6 , 9d 3 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 Mossbauer spectra of the (R 1− x R′ x ) 2 Fe 16 Co 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.

Fe/Tb multilayers of fixed Tb thickness (1.9 nm) and various Fe thichnesses (in the range 0.2-3.3 nm) have been prepared by rf-pulverization on Si(111) substrates. Conversion Electron Mossbauer Spectrometry was used to get information on the structure and the spin texture of the multilayers. Polar Kerr hysteresis loops have been used to obtain the global magnetic properties. The iron layers are amorphous up to 2.1 nm and the magnetic anisotropy lies in the plane of the layers above e Tb /e Fe =0.9