Engineering Magnetic Hybridization at Organic-Ferromagnetic Interfaces by C-60-Adsorption-Induced Fe(001) Surface Reconstruction

Large magnetoresistance has been reported for C-60-based vertical spin valves. But for the underlying organic-ferromagnetic interfacial atomistic structures, both experimental and theoretical works have assumed unreconstructed atomic structures for the magnetic surfaces, although organic molecule (e.g., fullerene and thiolate) adsorption frequently induces nonmagnetic surfaces reconstruction. Here we report that C-60 adsorption can induce a prototype ferromagnetic surface, Fe(001), reconstruction, via thorough structural search from first-principles calculations. We propose that Fe(001) surface reconstruction should already occur under the reported annealing temperature in literature. Reconstruction solidifies C-60/Fe interface bonding and enhances C-60 spin-polarization. More importantly, only our reconstructed structure can explain the experimental observation of an inversion of C-60 spin-polarization around Fermi-level relative to that of Fe substrate, which is attributed to the C-60 lowest unoccupied molecular orbitals LUMO-derived states are shifted to Fermi level by charge transfer and to the strong coupling in the reconstructed structure. One could expect that surface reconstruction occur not only at the C-60/Fe(001) interface, but also at interfaces of other molecule-magnetic metals. Hence our work offers a new pathway to interface engineering, that is, via surface reconstruction to manipulate spintronic properties and promote the field of interface-assisted spintronics.