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.