Electronic and magnetic structure of C60/Fe3O4(001): a hybrid interface for organic spintronics

We report on the electronic and magnetic characterization of the hybrid interface constituted of C-60 molecules and an epitaxial Fe3O4(001) surface grown on GaAs(001). Using X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD), we demonstrate that a stable C-60 sub-monolayer (ML) can be retained on the Fe3O4(001) surface upon in situ annealing at 250 degrees C. A carbon K-edge dichroic signal of 1% with respect to the XAS C 1s -> pi* peak intensity has been observed, indicative of a weaker electronic interaction of C-60 with Fe3O4(001) compared to the previously reported case of C-60/Fe(001). Remarkably, the Fe L-edge XMCD spectrum of Fe3O4(001) reveals a reduced Fe3+/Fe2+ ratio upon C-60 sub-ML adsorption. This observation has been ascribed to electron donation by the C-60 molecules, as a consequence of the high work function of Fe3O4(001). Our present work underlines the significance of chemical interactions between inorganic magnetic surfaces and molecular adsorbates for tuning of the electronic and magnetic properties of the interfaces, which have a profound impact on spin-polarized charge transport in hybrid organic-inorganic spintronic devices.