THE FIELD-DEPENDENCE OF THE HYPERFINE SPLITTING OF TERBIUM IN TBNI5

The hyperfine splitting of the ground state of terbium in a single cry stal of TbNi5 has been studied using Tb-159 spin-echo NMR at 1.3 K and in fields up to 8 T. The measurements are in perfect agreement with c omputations including corrections for the effect of J-mixing. From the field dependence of the quadrupolar splitting we have derived the ele ctric field gradient at the terbium nucleus: V-cc('') = (9.77 +/- 0.2) x 10(21) V m(-2) and the ratio of antishielding factors: gamma N/gamm a E = 174 +/- 6. The value obtained for gamma N/gamma E is significant ly different from that measured for the insulating compound Tb(OH)(3). The contributions of the spin- and orbitally polarized conduction ele ctrons to the total hyperfine field: B-ce = 3.17 T and B-orb = 0.63 T are obtained from the held dependence of the dipolar splitting.