Theoretical study of hyperfine fields at impurity nuclei in GdX (X=Zn,Cd) compounds: A two center model

We theoretically discuss the local moment formation and the hyperfine field behavior of nonmagnetic (s-p and noble) impurities diluted in ferromagneti c rare-earth compounds GdX (X = Zn, Cd). It is experimentally observed in t hese systems that all impurities enter substitutionally at the "nonmagnetic " X lattice site, creating a strong local charge perturbation. In our simpl ified model, one calculates the local magnetic moment in the perturbed cond uction band at the origin (a charge perturbed X site). The polarization of the conduction band arises from the Gd 4f moments and the conduction electr on polarization produced by the host magnetic moment at the origin is treat ed within the Born approximation. The general trend of the experimental hyp erfine field data is well reproduced by our self-consistent calculations. ( C) 1998 American Institute of Physics. [S0021-8979(98)40111-7].