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

In the intermetallic compound YFe2, the metallic hyperfine field at th e 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 t ransferred hyperfine interaction, we have performed first-principles c alculations, within the local spin-density theory, for embedded cluste rs 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 hyperfi ne field and the dipolar field were obtained; the resulting total fiel d was found to increase with the spin of the rare-earth impurity. Orbi tal hyperfine fields were not considered. The contact transferred fiel d was found to arise from direct polarization of the s electrons by th e rare-earth spin.