ABINITIO CALCULATION OF MOLECULAR-FIELD INTERACTIONS IN RARE-EARTH TRANSITION-METAL INTERMETALLICS

The interaction, K(RM), between the rare-earth 4f moment and the transition-metal 3d moments in rare-earth transition-metal intermetallics is shown to depend upon the R-5d moment, which is due to 3d-5d hybridization, and local 4f-5d exchange integrals. Both the R-5d moment and K(RM) may be calculated ab initio from the local spin-density approximation to density functional theory in self-consistent energy-band calculations with the localized 4f-moments fixed at their Russel-Saunders values. Detailed examples are given for the RFe2 (R = Gd - Yb) series. The exchange integrals are similar to those entering into the density functional version of Stoner theory and their energy dependence must be treated carefully. The calculated local exchange integrals are shown to be related to the molecular fields derived from spin Hamiltonians, hence to the spin-wave spectra. Reasonable agreement with values of the molecular fields extracted from inelastic neutron scattering and high field susceptibility measurements is obtained.