Spin filtering at organic-metal interfaces is often determined by the details of the interaction between the organic molecules and the inorganic magnets used as electrodes. In a recent paper published in Nature Communication we have demonstrated a spin-filtering mechanism based on the dynamical spin relaxation of the long-living interface states formed by the magnet and weakly physisorbed molecules. We have investigated the case of Alq3 on Co and, by combining two-photon photoemission experiments with electronic structure theory, showed that the observed long-time spin-dependent electron dynamics is driven by molecules in the second organic layer. The interface states formed by physisorbed molecules are not spin-split, but acquire a spin-dependent lifetime, that is the result of dynamical spin-relaxation driven by the interaction with the Co substrate. Such spin-filtering mechanism has an important role in the injection of spin-polarized carriers across the interface and their successive hopping diffusion into successive molecular layers of molecular spintronics devices.
The paper can be found in Nature Communication 7, 12668 (2016) and it was the result of a long-standing collaboration between the Computational Spintronics Group and the group of Mirko Cinchetti and Martin Aeschlimann.