155Gd Mössbauer spectroscopy study of the Gd2Fe17Hx system

Abstract 155 Gd Mossbauer spectroscopy experiments have been undertaken on the Gd 2 Fe 17 H x ( x = 0, 3, 5) series and the results are analysed in the light of the structural and magnetic characteristics of these compounds. In contrast to carbon or nitrogen insertion, hydrogen is found to lower the positive electric field gradient ( V zz ) at the Gd nuclei. A decrease of the crystal field induced anisotropy is anticipated in the R 2 Fe 17 H x compounds. The reduction of the hyperfine field upon hydrogenation is attributed to a decrease of the (positive) field due to the conduction electron polarization. The larger isomer shift observed in the hydrides is assigned to a charge transfer from the Gd 6s orbital onto the H atoms.