Magnetic circular x-ray dichroism (MCXD) studies at L2 3 absorption edges in intermediate-valence (IV) compounds CeFez, Ce(Feo sCop g)2 CeCo"CezCo, 7, and trivalent 4f ' systems (CeRuzGe2, Ce3A1», CePd, CeFe2H3 8) at the Ce L2 3 edges are presented. The comparison with reference compounds (La, Lu, Hf, Cxd) confirms the existence, in such IV systems, of an ordered Sd magnetic moment on the Ce site antiferromagnetically coupled with the 3d Fe (Co) moment. Moreover, this study suggests, provided the 4f orbital moment is almost quenched, the existence of a simple proportionality between the MCXD intensity and the magnetic moment of the probed atom. For instance the MCXD method leads to a Ce Sd magnetic moment in CeFe~of about 0.3Sp& antiferromagnetically coupled with the 3d Fe moment, in good agreement with band-structure calculations. The MCXD applications in Ce(Fe, Co)2 and CeFe2H" permit us to define precisely the electronic structure of Ce in such compounds. Particularly we will show that MCXD experiments at the L2 3 absorption edges of Ce are able to yield valuable information on the degree of hybridization of the 4f electrons in the ground state. Indeed, systematic comparison between the MCXD signals of IV and normal trivalent Ce compounds reveals the extreme sensitivity of the L2 3 MCXD experiments to the degree of localization of the 4f electrons.

By following the experimental results recently published about electronic-energy-deposition-induced effects in metallic materials, a mixing effect is observed in an Fe/Si multilayer irradiated by 650 MeV uranium ions. Mössbauer spectroscopy shows that, after a fluence as low as 1013 cm-2, an Fe 4.5 nm/Si 3.5 nm multilayer has been made almost homogeneous by ion mixing. On electron micrographs, at very low fluence, latent tracks are observed where the magnetic properties are drastically modified from the previous crystalline ferromagnetic state.

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