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Molecular spintronics with functionnal molecules

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Organic materials (with light elements like C, N, O or H) are excellent candidates for the next generation of all-spin logic devices [1] for which the steps of storage and propagation of the spin information are crucial. Thanks to the weak spin scattering (weak spin-orbit coupling and weak hyperfine interactions) present in those materials, long spin lifetime have been predicted (up to the ms against few ns or ps in metals)[2]. Carbon nanotubes and graphene present moreover a high mobility for the charge carriers which would allow transport of this information over long distances [3]. Finally, it has been shown very recently that molecules tend to hybridize at the interface with a ferromagnetic metal [5-5]. This hybridization allows a complete modulation of spin injection properties (spin polarization of the injected current... see the following review to understand what is the spin polarization here.).

Up to now, molecules were mainly used as tunnel barrier or propagating layer for the spin polarized current in organic magnetoresistive devices like ferromagnetic metal/molecules/ferromagnetic metal [6].
Our research is oriented toward the use of functionnal molecules like for instance, molecular diodes or spin transitions molecules in order to study spin dependent transport phenomena in hybrid devices and to look for new spintronics functionnalities. The integration of graphene and carbon nanotubes is also investigated.

Figure 1a : Scheme of a molecular magnetic junctions. The magnetization of the ferromagnetic layers is represented by the black arrows. Figure 1b : Magnetoresistance effect in a magnetic junction. The different configurations of the magnetizations are also drawn. The magnetoresistance effect is defined as the relative difference between the resistance in the antiparallel configuration of the magnetizations and the resistance in the parallel state.

[1] B. Behin-Aein et al., Nature Nanotechnology 5 266-270 (2010)

[2] S. Sanvito & A. R. Rocha, Journal of Computational and Theoritical Nanoscience 3 624-642 (2006)

[3] P. Seneor et al., MRS Bulletin 37 1245-1254 (2013)

[4] C. Barraud et al., Nature Physics 6 615-620 (2010)

[5] One paper from the STM group here at MPQ
S.L. Kawahara et al., Nanoletters 12 4558 (2012)

[6] V. Dediu et al., Nature Materials 8 707-716 (2009)

A review in French about spin electronics is available here.
An other review in English is available here.
Finally, a review about spin polarized tunneling is given here.