COMPETING EXCHANGE INTERACTIONS IN FERROMAGNETIC CEFE2

We have measured the dispersion curves of the Fe spin-wave mode in the itinerant ferromagnet CeFe2 (T-C = 235 K). The only mode observed is that involving the Fe sublattice. The Fe mode has a gap of similar to 0.2 meV at the magnetic zone center. which is independent of temperatu re, and the spin-wave stiffness is similar to 150 meV Angstrom(2) at s mall q, a value of about half that found in YFe2 and all other rare-ea rth-Fe-2 compounds. The most unusual feature is that the dispersion al ong the [1 1 1] direction has another minimum at q = [1/2 1/2 1/2]. Th is observation implies that there are also strong antiferromagnetic fl uctuations in this material. (C) 1998 Elsevier Science B.V. All rights reserved.