报告题目:Topological Spin Dynamics for GreenIT

报  告  人:Mathias Klaui,Institut für Physik and Graduate School of Excellence Materials Science in Mainz, Johannes Gutenberg-Universitat Mainz, Mainz, Germany

报告时间:2018-10-19 14:00

报告地点:物理系理科楼C302

报告摘要:In our information-everywhere society IT is a major player for energy consumption. Novel spintronic devices can play a role in the quest for GreenIT if they are stable and can transport and manipulate spin with low power. Firstly to obtain ultimate stability, topologically stabilized spin structures, such as chiral domain walls and skyrmions can be used [1-3]. We have investigated in detail their dynamics and find that it is governed by the topology of their spin structures [1]. By designing the materials, we can even obtain a skyrmion lattice phase as the ground state of the thin films [2]. By analyzing the thermal energy landscape, we find that depending on the parameters (field, temperature, etc.), stripe domain or skyrmion phases constitute the lowest energy state [3]. Secondly, for ultimately efficient spin manipulation, we use spin-orbit torques: we combine ultimately stable skyrmions with spin orbit torques into a skyrmion racetrack device [2,4], where the real time imaging of the trajectories allows us to quantify the novel skyrmion Hall effect [4,5]. By studying the temperature dependence of the skyrmion Hall effect, we identify the acting mechanisms that lead to different dependences of the skyrmion Hall angle on the current density for the creep and the viscous flow regime [4,5]. Finally, we recently observed thermally activated skyrmion dynamics showing that skyrmions exhibit diffusion and this is applied to a skyrmion reshuffler device for stochastic computing [6].

[1] F. Büttner et al., Nature Phys. 11, 225 (2015).

[2] S. Woo et al, Nature Mater. 15, 501 (2016).

[3] I. Lemesh et al., Adv. Mater. (in press 2018).

[4] K. Litzius et al., Nature Phys. 13, 170 (2017).

[5] W. Jiang et al., Nature Phys. 13, 162 (2017)

[6] J. Zazvorka et al., arXiv:1805.05924