Systematics of Hyperfine Fields at Impurity Nuclei in Ferromagnetic Rare Earth Compounds GdZn and GdCd

The hyperfine (hf) fields at the nuclei of N, Ge, TI, V and Fe impurities in ferromagnetic GdZn and GdCd have been measured by NMR and Mossbauer methods. The results, together with the reported ones, nearly complete the systematics of the hf fields at sp and 3d impurities in GdZn(Cd). The hf fields at 4sp, 5sp and 6sp impurities are always negative, exhibiting a similar variation with increasing the impurity valence. The trend of the hf fields at 3 d impurities shows local moment contributions to the hf field at the middle of the 3d series, indicating finite local moments on Mn and Fe impurities. These results are found to resemble the systematics of the hf fields at impurities in Gd and are qualitatively explained by the theory of the hf field developed for Fe and Ni hosts.