HYPERFINE SPLITTING OF TERBIUM IN TB2FE17CX

We have studied the zero-field hyperfine splitting of Tb-159 in ferrim agnetic Tb2Fe17Cx (x = 1, 1.5, 2) using spin-echo NMR at 4.2 K. Distin ct spectra arising from the different sites characterized by the numbe rs of carbon nearest neighbours (NN = 0, 1, 2, 3) are observed. The me asured hyperfine parameters u(t) and P-t for all four spectra are give n for x = 1.5 and 2. Analysis of the quadrupolar splitting indicates t hat in Tb2Fe17C1.5 the dominant contribution to the magnetocrystalline anisotropy arises from the NN = 3 sites.