Electronic and magnetic structure of C₆₀Fe₃O₄(001): A hybrid interface for organic spintronics

We report the electronic and magnetic characterization of the hybrid interface constituted by C60 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 C60 sub-monolayer (ML) can be retained on the Fe3O4(001) surface upon in-situ annealing at 250°C. A carbon K-edge dichroic signal of 1% with respect to the XAS C 1s → π* peak intensity has been observed, indicative of a weaker electronic interaction of C60 with Fe3O4(001) compared to the previously reported case of C60/Fe(001). Remarkably, the Fe L-edge XMCD spectrum of Fe3O4(001) reveals a reduced Fe3+/Fe2+ ratio upon C60 sub-ML adsorption. This observation has been ascribed to electron donation by the C60 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 the electronic and magnetic properties of the interfaces, which have profound impact on spin-polarized charge transport in hybrid organic-inorganic spintronic devices.