Spin-polarized electron transfer in ferromagnet/C60 interfaces

The contact between a molecule and a metallic electrode contributes to or even determines the characteristics of organic devices, such as their electronic properties. This is partly due to the charge transfer that takes place when two materials with different chemical potentials are put together. In the case of magnetic electrodes, the transfer can be accompanied by the transmission of a net spin polarization or spin doping. In nanocarbon systems, hybridization and spin doping can suppress the moment of a transition metal ferromagnet through the loss of majority spin electrons to the organic. Here, C-60 is shown to become ferromagnetic as a result of spin doping from cobalt with an induced moment of 1.2 mu(B) per cage while suppressing the moment of the ferromagnet by up to 21%. Polarized neutron reflectivity and x-ray magnetic circular dichroism reveal the presence of an antiferromagnetic coupling of the interfacial layers of cobalt and C-60, and weakly coupled induced magnetism propagating into the bulk organic. Thus, it is shown that the deposition of molecules with high electron affinity can be used to induce zero-voltage spin injection.