Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 61: Poster II: Materials, Interfaces and Heterostructures

HL 61.8: Poster

Thursday, March 25, 2010, 18:00–20:00, Poster D1

Spin Transport and Spin Precession in Bilayer Graphene with Transparent Ferromagnetic Contacts — •Bastian Birkner, Dieter Weiss, and Jonathan Eroms — Institut für Experimentelle und Angewandte Physik, Universität Regensburg

We achieved electrical spin injection with a DC current from a ferromagnetic material (Co) into bilayer graphene without using any tunnel barrier. This results in a contact resistance of about 450 Ohm which indicates that the junctions between the Co and graphene are transparent. The graphene flakes were mechanically exfoliated from natural graphite by using adhesive tape. The induced spin accumulation diffuses away from the injection point and is probed in a non-local four terminal scheme where charge and spin current are completely separated from each other. We obtain a clear spin signal R_nl=U_nl/I whose sign depends on the magnetization orientation (parallel/antiparallel) of the ferromagnetic electrodes. By applying a perpendicular magnetic field we also detected spin precession (Hanle effect) that confirms that the non-local signal originates from spin injection and spin transport. Fitting of Hanle curves yields a spin relaxation time in the range of 60-130 ps and a spin diffusion length of below one micrometer. The polarization was estimated to be less than 5 percent.