Magnetism of RFe2 compounds

The combination of itinerant transition metal (M=Fe) and localized rare earth (R=Gd-Yb) magnetism in RFe2 compounds has been investigated in self-consistent energy band calculations. The computed and measured total moments are in good agreement. We find, however, that there is a significant contribution to the moment from the R-5d partial moments coupled antiparallel to the Fe-3d moment which results from 3d-5d hybridization. The R-4f moments interact with the conduction band system solely by local exchange interactions which are calculated ab initio from density functional theory. A sum rule for the total 3d+5d moment is shown to be obeyed and an expression for the effective ferrimagnetic exchange interaction between 3d and 4f electrons is derived.