The gadolinium-hydrogen system

Abstract

Isomer shifts have been measured above and below the Néel temperature (21 K) for the dihydride phase of the gadolinium-hydrogen system at different H : Gd ratios using a ¹⁵⁵Gd source. No evidence has been obtained for a quadrupole contribution to the observed spectra. The hyperfine magnetic field at the gadolinium nucleus within the dihydride phase range GdH_1.8 to GdH_2.3 does not change significantly with change in hydrogen content. Differences in the hyperfine magnetic-field strengths for GdH₂ and other metal-like gadolinium compounds are attributed to neighbour effects and possibly a large covalent contribution by hydrogen to the hyperfine magnetic field at the gadolinium nucleus. A comparison is made between the experimentally determined electric-field gradient in GdH₃ and values obtained by calculation using a point-charge model; the results clearly point to the anionic character of the hydrogen.