TRANSFERRED HYPERFINE FIELDS IN RARE-EARTH-SUBSTITUTED YFE2 AND YNI2

In the intermetallic compound YFe2, the metallic hyperfine field at the Y nucleus, as measured by Y-89 NMR spectroscopy, is affected by the substitution of one or more neighbour Y atoms by different rare-earth impurities. In order to understand the underlying mechanisms for the transferred hyperfine interaction, we have performed first-principles calculations, within the local spin-density theory, for embedded clusters representing a Y atom and its vicinity in the compounds Y1-xRxFe2 (R = Gd, Th, Ho, Tm or Lu) and Y1-xGdxNi2. The contact magnetic hyperfine field and the dipolar field were obtained; the resulting total field was found to increase with the spin of the rare-earth impurity. Orbital hyperfine fields were not considered. The contact transferred field was found to arise from direct polarization of the s electrons by the rare-earth spin.