A spin echo study of the 59Co hyperfine field in GdCo2 and several related series of substitutional compounds

The hyperfine fields at the 59 Co nucleus have been observed in GdCo 2 (GdY)Co 2 , (GdDy)Co 2 and Gd(CoNi) 2 using a spin echo technique. The field strength in the basic compound GdCo 2 was found to be 60·7 kOe. The results can be interpreted in terms of contributions to the hyperfine field arising from the transition metal sublattice and from the rare earth sublattice. The former appears to be proportional to the magnetic moment associated with the transition metal ion while the rare earth contribution is taken to arise predominantly from conduction electron polarization. With yttrium substitution this second term is found to be directly proportional to the gadolinium concentration. In the nickel substituted compounds the hyperfine field due to the rare earth sublattice is observed to decrease. This is believed to be the result of a change in conduction electron concentration.