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PGI Kolloquium:

Prof. Dr. Ulrich Nowak,
University of Konstanz, Konstanz, Germany


PGI Lecture Hall, Building 04.8, 2nd Floor, Room 365

10.01.2020 11:00 Uhr

Modeling skyrmion diffusion in thin film

BildCopyright: Prof Dr. Novak

Skyrmions are topologically protected magnetic textures that can appear in ferromagnetic thin-films multilayers. As mobile quasi particles they are increasingly discussed as possible building blocks for spintronic applications. In a combined experimental and theoretical study we investigated Skyrmion diffusion [1], an effect that limits deterministic Skyrmion dynamics. While hence being of fundamental interest we also showed that Skyrmion diffusion can also serve as an operation mechanism for devices needed for probabilistic computing [1].

In this talk we will introduce a multi-scale scheme to investigate thermal Skyrmion dynamics, starting from first princples and going via spin model simulations to mesoscopic approaches via the Thiele equation which describes the Skyrmion effectively as rigid structure. We derive a spin model for a PtIr/Fe-bilayer on a Pd surface from first principles and simulate its behavior via the stochastic Landau-Lifshitz-Gilbert equation to investigate diffusive motion of Skyrmions. In that model the frustration of the isotropic exchange interactions in connection with the Dzyaloshinskii-Moriya interaction is responsible for the creation of skyrmionic structures with various topological charges [2].

We investigate the dependence of the diffusive motion on the topological properties and show that a deviation of the Skyrmion's shape from perfectly round can lead to an anisotropic dynamics [3] and, eventually, anisotropic diffusion.

[1] Zázvorka et al., Nat. Nanotech. 14, 658 (2019)
[2] Rózsa et al., Phys. Rev. B 95, 094423 (2017).
[3] Weißenhofer and Nowak, Phys. Rev. B 99, 224430 (2019).


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