Abstract
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. Here we demonstrate 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 investigate the case of Alq3 on Co and, by combining two-photon photoemission experiments with electronic structure theory, show 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.
Highlights
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 the simpler case of interfaces formed between organic molecules and non-magnetic materials depicted in Fig. 1a, Baldo and Forrest described charge injection in terms of a two-step process, where charges are initially injected into hybrid interface states (HISs) close to the Fermi energy and successively hop from the interfacial region into the bulk distribution
Together with those recently published by Raman et al.[40] demonstrate that, while much research effort has been concentrated on strengthening the chemisorption process for molecules on FM substrates[35,36], the design of weakly coupled organic layers to be deposited on top of spinterfaces may represent a different strategy for tuning the spin-dependent transport characteristics of molecular spintronic devices in both the tunnelling as well as the injection/hopping regimes
Summary
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. 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. This gives rise to the so-called interface magneto-resistance effect, which was recently observed in devices with only one magnetic electrode[40]. Together with those recently published by Raman et al.[40] demonstrate that, while much research effort has been concentrated on strengthening the chemisorption process for molecules on FM substrates[35,36], the design of weakly coupled organic layers to be deposited on top of spinterfaces may represent a different strategy for tuning the spin-dependent transport characteristics of molecular spintronic devices in both the tunnelling as well as the injection/hopping regimes
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