Hyperfine fields at lanthanide nuclei in the intermetallic compounds of RFe₂

We have measured the hyperfine fields of ¹⁶⁹Tm in Tm_0.02Gd_0.98Fe₂ and Tm_0.02Gd_0.98Fe₂ compounds using spin-echo NMR at 4.2 K. The results, together with complementary data obtained from other sources, are interpreted in terms of a simple model which involves hyperfine fields transferred from the lanthanide and iron ions. The effects of crystal-field quenching of the rare-earth moments in RFe₂ (R = heavy rare earth) and, where appropriate, magnetostriction, are estimated. We show that our simple model is satisfactory in the interpretation of hyperfine fields at lanthanide nuclei in the RFe₂ compounds. We obtain the coefficients K_p = 9.4(1.4) T, K_n = 3.5(0.9) T and β = 15.8(1.6) T μ_B^-1.