The field dependence of the hyperfine splitting of terbium in TbNi₅

The hyperfine splitting of the ground state of terbium in a single crystal of TbNi₅ has been studied using ¹⁵⁹Tb spin-echo NMR at 1.3 K and in fields up to 8 T. The measurements are in perfect agreement with computations including corrections for the effect of J-mixing. From the field dependence of the quadrupolar splitting we have derived the electric field gradient at the terbium nucleus: V″_cc = (9.77 ± 0.2) × 10²¹ V m^-2 and the ratio of antishielding factors: γ_N/γ_E = 174 ± 6. The value obtained for γ_N/γ_E is significantly different from that measured for the insulating compound Tb(OH)₃. The contributions of the spin- and orbitally polarized conduction electrons to the total hyperfine field: B_ce = 3.17 T and B_orb = 0.63 T are obtained from the field dependence of the dipolar splitting.