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MA: Fachverband Magnetismus

MA 66: Poster 3

MA 66.23: Poster

Freitag, 24. März 2017, 09:30–13:00, P2-OG2

Ultrafast spin dynamics in CoFeB/MgO/CoFeB magnetic tunnel junctions — Leon Duschek, •Jakob Walowski, Christian Denker, Ulrike Martens, and Markus Münzenberg — Ernst-Moritz-Arndt Universität, Greifswald

Magnetization dynamics in CoFeB layers with out-of-plane magnetic anisotropy (PMA) separated by a crystalline MgO isolating layer are probed in all-optical pump-probe experiments.
In 2013 He et al. [1] have shown, that the laser excitation in such layer systems can induce an exchange of spins through the MgO barrier. Extending those measurements to samples with patterned circular structures with diameters from 1 µ m to 5 µ m enables the observation of both processes in individual MTJs. Due to the small sizes and a crystalline structure, the exchange of spins through the MgO barrier takes place by coherent tunneling. The investigated magnetic layers have thicknesses from 0.9 µ m to 1.3 µ m, to ensure PMA. The dynamics are probed using both, the Kerr rotation and ellipticity. Because the stacks are thinner than the penetration depth of the laser light, each component provides the information at different depths of the layer stack [2]. Thus we observe the dynamics from both magnetic layers individually, gaining insight into the processes inside, which stem from spin-flip scattering and from spin-polarized transport. Both, the spin dynamics and the spin transport depend on the properties of the magnetic electrodes and the tunnel barrier.
W. He et al., Scientific Reports 3, 2883 (2013)
J. Wieczorek et al., PRB 92, 174410 (2015)