Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 43: Spintronics (joint session HL/TT)

HL 43.3: Talk

Thursday, March 15, 2018, 15:30–15:45, EW 201

Measuring Anisotropic Spin Relaxation in Graphene — Sebastian Ringer, Stefan Hartl, Matthias Rosenauer, Tobias Völkl, Maximilian Kadur, Franz Hopperdietzel, Dieter Weiss, and •Jonathan Eroms — Institute of Experimental and Applied Physics, University of Regensburg, Germany

To measure the anisotropy of the spin-lifetime in graphene, the most notable experiments are out-of-plane rotation of the ferromagnetic electrodes and oblique spin precession. We present a third method which is a Hanle experiment where the electron spins precess around either a magnetic field perpendicular to the graphene plane or around an in plane field. In the latter case, electrons are subject to both in-plane and out-of-plane spin relaxation.

To fit the data, we use a numerical simulation that can calculate precession with anisotropies in the spin-lifetimes under magnetic fields in any direction. Our data show a small, but distinct anisotropy that can be explained by the combined action of isotropic mechanisms, such as relaxation by the contacts and resonant scattering by magnetic impurities, and an anisotropic Rashba spin-orbit based mechanism.

We also perform oblique spin precession on our sample and compare it to our experiment of in-plane/out-of-plane Hanle in terms of reliability and precision. We find a non-trivial magnetization in our contacts that was only detected in the in-plane/out-of-plane Hanle experiment but is essential for a correct analysis of the oblique spin precession data. We conclude that the in-plane/out-of-plane Hanle experiment is the most reliable and precise method to measure the anisotropy.