Investigation of the magnetic hyperfine field of 181Ta in the rare earth Laves phases RCo2

The magnetic hyperfine field Bhf of the 5d probe 181Ta on cubic R sites of the C15 Laves phases RCo2 has been determined at 10 K by perturbed angular correlation spectroscopy for heavy (Gd, Tb, Dy, Ho, Er, Tm) and light (Sm, Nd, Pr) R constituents. For heavy R constituents, Bhf(181Ta/RCo2) is found to increase with the R atomic number, similar to the trend found for the closed-shell probe 111Cd in RCo2, but opposite to the decrease of Bhf previously reported for the 5d probe 181Ta in RFe2. Qualitatively, these opposite trends can be related to the differences in the R dependence of the 3d moments of RCo2 and RFe2. e light R constituents, the variation of Bhf(181Ta/RCo2) with the R atomic number is almost twice as strong as for the heavy R constituents reflecting a stronger d–f interaction due to the larger radial extension of the 4f wave function of the light R.