Magnetic hyperfine fields at¹¹⁹Sn probe nuclei on the R sites of the cubic rare-earth Laves-phase compounds RFe₂and RCo₂

Abstract

The magnetic hyperfine interaction of the 119Sn probe nucleus on the R site of the ferro- and ferrimagnetic RFe2 (R = Sm–Tm, Lu, Zr, Hf and U) and RCo2 (R = Gd–Er) compounds has been investigated by Mössbauer spectroscopy technique. It was found that the magnetic hyperfine fields (Bhf) exhibit quite different behaviours in the two series of the compounds. For the RFe2 compounds, the ratio Bhf/μ3d remains essentially constant across the series at a value of 30 T/μB (within ± 4%), also for nonmagnetic R = Zr, Lu and Hf. This means that a contribution to Bhf from the 4f magnetic moments of the R sublattice is absent. In RCo2 compounds, the total hyperfine field is the sum of two contributions: one is the 4f contribution (B4f) and the other is 3d contribution (B3d). The 3d and 4f contributions have the same relative sign; both contributions are positive with respect to the 3d moments direction. The B4f contribution is relatively large: the ratio B4f/B3d varies from about 0.4 (ErCo2) to about 0.7 (GdCo2). The results demonstrate that the transfer of the electron polarization from the R atoms to the hybrid bonds is extremely sensitive to the features of the 3d electrons of the transition-metal subsystem.