  Spectra of x-ray absorption and magnetic circular dichroism were measured at
M4,5(3d) and L2,3(2p) edges of Ce in multilayers [Ce(1-x)Six/Fe]xn, with x
between 0.1 and 0.65. The study uncovers the highly correlated nature of this
layered system. An alpha-phase like electronic configuration of Ce is observed,
with ordered magnetic moments on the 4f and 5d electrons induced by the
interaction with Fe. Increasing the Si content reduces the strength of the
hy-bridization between the 4f and conduction-band states which is reflected in
a growing occupation and magnetic polarization of the 4f states. Variations of
the shape and intensity of the L2,3-edge dichroism spectra, discussed in a
simple phenomenological model, show the importance of the exchange interaction
between the Ce-4f and 5d electrons, spin polarized by the interaction with Fe
at the interfaces, for the electronic structure of Ce at high Si concentration
and low temperature. A model of the band structure of rare-earth
transition-metal compounds permits to argue that magnetic order on the Ce 4f
electrons in the multilayers is due to different mechanisms: to hybridization
of the Ce-4f with the Fe-3d states at low Si concentration and to intra-atomic
4f-5d exchange at high Si concentration. This is at variance with magnetic
order in the intermetallics CeSi2-delta and CeSi which results from interaction
between the localized 4f magnetic moments mediated by the Si-derived (s,p)
conduction electrons, in competition with the Kondo effect.
