Berlin 2018 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 4: Skyrmions I (joint session MA/KFM/TT)

KFM 4.1: Topical Talk

Montag, 12. März 2018, 15:00–15:30, EB 301

Structure, Energetics, and Deterministic Writing of Skyrmions in Thin Film Ferromagnets — •Felix Büttner — MIT, Cambridge, MA, USA

Room temperature skyrmions were recently observed in magnetic multilayer systems [1-4], most of them in materials with sizable Dyzaloshinskii-Moriya interaction (DMI). In this talk, I will present a unified theory that analytically describes the energy of such skyrmions, including stray fields [1]. We can now rigorously define two types of skyrmions, "stray field skyrmions" and "DMI skyrmions". DMI skyrmions can be sub-10 nm at zero field and room temperature and moved with velocities exceeding 1000 m/s at 10¹² A/m².

Experimentally, I will show that skyrmions can be nucleated by spin-orbit torque current pulses without any applied fields [2]. The nucleation mechanism is robust, ultra-fast (sub-nanosecond), and extremely easy to implement. I will discuss the mechanism of the skyrmion generation and explain why DMI can replace the need for in-plane fields.

[1] Büttner et al., Nat Phys. 11, 225 (2015). [2] Woo et al., Nat Mater. 15, 501 (2016). [3] Moreau-Luchaire et al., Nat Nano. 11, 444 (2016). [4] Boulle et al., Nat Nano. 11, 449 (2016). [5] Büttner et al., arXiv:1704.08489 [6] Büttner et al., Nat Nano. 12, 1040 (2017).