Magnetic hyperfine fields on 140Ce probes substituting for the rare earth in RCo2 laves phases

The magnetic hyperfine fields (MHF) acting on 140Ce probes substituting for the rare-earth sites in RCo2 Laves phases (R = Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm) were determined by perturbed angular correlation spectroscopy. The MHF scales very well with the Co magnetic moment throughout the series as already observed with 181Ta, and to a lesser extent, with 111Cd probes. It is shown that the orbital contribution to the MHF is about one order of magnitude smaller than in the free Ce+3 ion. The decrease was attributed to the de-localization of the Ce 4f electrons.