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Magnetoresistance effects in phthalocyanine based magnetic tunnel junctions

Clement Barraud 1Richard Mattana 1Pierre Seneor 1Raphael Guillemet 1Stephane Fusil 1Karim Bouzehouane 1Cyrile Deranlot 1Frédéric Petroff 1Albert Fert 1Jean Batiste Beaufrand 2Dong Jik Kim 2Jacek Arabski 2Samy Boukari 2Martin Bowen 2Eric Beaurepaire 2

1. Unité Mixte de Physique CNRS-Thales, Route départementale 128, Palaiseau 91767, France
2. Institut de Physique et Chimie des Materiaux de Strasbourg, UMR7504, CNRS - ULP, 23, rue du Loess, BP 43, Strasbourg CEDEX 2 67034, France

Organic spintronics has been the focus of a growing interest since 2002 and the first
observation of magnetoresistance effects through sexithiophene (T6) films [1]. Since then, most of the successful studies have dealt with aluminium tris(8-hydroxyquinoline) (Alq3) [2]. Here we report on the fabrication and magneto-transport properties of nanometer size organic magnetic tunnel junctions based on the cobalt-phthalocyanine organic semiconductor.
In order to elaborate these nanometer size tunnel junctions, the fabrication is carried out using a combination of UV lithography and conductive tip AFM nanoindentation process where the tip-sample resistance is monitored in real time [3]. With this technique, we are able to control the section (about few tenth nm2) of the nanocontact. Moreover, by indenting further, we can also vary the organic tunnel barrier thickness. As a final step, cobalt is deposited into the nanocontact forming a magnetic tunnel junction enabling the study spin dependent tunnelling through the CoPc layer.
We have performed spin dependent transport measurements in Co/CoPc/Co magnetic tunnel
junctions where the thickness of the organic semiconductor is only few nm. We have observed a significant magnetoresistance effect (>30 %) at low temperature. Two contributions to the magnetoresistance are isolated: a tunnel anisotropic magnetoresistance (TAMR) and a spin valve effect associated to the magnetic configuration of Co electrodes (parallel and antiparallel magnetic configurations).

[1] V. Dediu et al., Solid State Communication, 122, 181 (2002)
[2] Z.H. Xiong et al., Nature, 427, 821 (2004); L.E. Hueso et al., Adv. Mater. 19, 2639 (2007); T.S Santos et al., Phys. Rev. Lett. 98, 016601 (2007); H. Vinzelberg et al., J.Appl. Phys. 103, 093720 (2008)
[3] K. Bouzehouane et al. Nanolett. 3 1599 (2003)


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Presentation: Poster at E-MRS Fall Meeting 2009, Symposium E, by Clement Barraud
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-25 17:27
Revised:   2009-06-07 00:48