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Towards molecular spintronics

Abstract

The ability to manipulate electron spin in organic molecular materials offers a new and extremely tantalizing route towards spin electronics, both from fundamental and technological points of view. This is mainly due to the unquestionable advantage of weak spin–orbit and hyperfine interactions in organic molecules, which leads to the possibility of preserving spin-coherence over times and distances much longer than in conventional metals or semiconductors. Here we demonstrate theoretically that organic spin valves, obtained by sandwiching an organic molecule between magnetic contacts, can show a large bias-dependent magnetoresistance and that this can be engineered by an appropriate choice of molecules and anchoring groups. Our results, obtained through a combination of state-of-the-art non-equilibrium transport methods and density functional theory, show that although the magnitude of the effect varies with the details of the molecule, large magnetoresistance can be found both in the tunnelling and the metallic limit.

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Figure 1: Structural and electronic properties of a Ni(001)/octane/Ni(001) spin-valve.
Figure 2: Structural and electronic properties of a Ni(001)/tricene/Ni(001) spin-valve.
Figure 3: Magneto-transport properties of a Ni(001)/octane/Ni(001) spin-valve.
Figure 4: Magneto-transport properties of a Ni(001)/tricene/Ni(001) spin-valve.
Figure 5: Orbital-resolved density of states for a tricene molecule attached to nickel electrodes as a function of the distance between the sulphur atom and the nickel hollow site.

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Acknowledgements

This work is sponsored by the Science Foundation of Ireland under the grant SFI02/IN1/I175, the UK EPSRC and the EU network MRTN-CT-2003-504574 RTNNANO. J.F. and V.M.G.S. thank the Spanish Ministerio de Educacíon y Ciencia for financial support (grants BFM2003-03156 and AP2000-4454). A.R.R. thanks Enterprise Ireland (grant EI-SC/2002/10) for financial support. Travel has been sponsored by the Royal Irish Academy under the International Exchanges Grant scheme. We thank J. H. Jefferson for discussions.

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Correspondence to Stefano Sanvito.

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Rocha, A., García-suárez, V., Bailey, S. et al. Towards molecular spintronics. Nature Mater 4, 335–339 (2005). https://doi.org/10.1038/nmat1349

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