GD-155 MOSSBAUER-SPECTROSCOPY STUDY OF THE GD2FE17HX SYSTEM

Gd-155 Mossbauer spectroscopy experiments have been undertaken on the Gd2Fe17Hx (x = 0, 3, 5) series and the results are analysed in the lig ht of the structural and magnetic characteristics of these compounds. In contrast to carbon or nitrogen insertion, hydrogen is found to lowe r the positive electric field gradient (V(zz)) at the Gd nuclei. A dec rease of the crystal field induced anisotropy is anticipated in the R2 Fe17Hx compounds. The reduction of the hyperfine field upon hydrogenat ion is attributed to a decrease of the (positive) field due to the con duction 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.