ANALYSIS OF THE MAGNETIC-BEHAVIOR OF CE1-XGDXCO2 COMPOUNDS

Experimental data on the spontaneous magnetization m(s)(T) of Ce1-xGdx Co2 compounds were analysed using a mean-field phenomenological model which takes into account the exchange interactions between atoms of th e three magnetic species (Gd, Ce, Co) as well as the crystal electric field interaction on the Ce ions, This model allowed us to obtain, thr ough a numerical fitting procedure to the m(s)(T) curves, the composit ion dependence of the Gd-Co and Go-Co exchange interaction strengths ( A(Gd-Co) and A(Co-Co), respectively) and of the Co magnetic moment m(C o). Both A(Gd-Co) and A(Co-Co) increase considerably with the Ce conte nt, while m(Co) decreases linearly from x = 1 down to the composition x = 0.15; below the latter value of x, the magnetic ordering is suppre ssed. The intermediate valence of Ce, as suggested by the composition dependence of the room temperature lattice parameter, being also compa tible with the obtained thermal variation of the Ce contribution to th e total magnetic moment, is expected to play an important role in the enhancement of the A(Gd-Co) and A(Co-Co) interaction strengths, throug h a net reinforcement of the 3d-5d hybridization. (C) 1998 Elsevier Sc ience B.V. All rights reserved.