L-edge inner shell spectroscopy of nanostructured Fe3O4

We have measured magnetic circular dichroism at the Fe L edge in samples of colloidal Fe3O4 and in Fe3O4 powder. The results for the colloid can be interpreted in terms of the model presented by Sette et al. for the dichroism of bulk Fe3O4, We notice a shift in the position of the Fe L-3 line in the colloid with regard to the powder, which is however in the opposite direction as expected for a cluster. We observe a new structure in the dichroism of the colloid spectrum that could be cluster-specific, in spite of the fact that, for the cluster size of our colloids, the fraction of atoms at the surface of the cluster is not large. (C) 2001 Elsevier Science B.V. All rights reserved.