题目： Topologically protected Spin Textures at Metal Surfaces

报告人：Prof.  Stefan Blügel 教授
            Peter Grünberg Institut and Institute for Advanced Simulation, 
            Forschungszentrum Jülich and JARA, Jülich, Germany
            s.bluegel@fz-juelich.de 

时间： 2016年4月18（周一）  上午9:00 

地点： 李薰楼468室

Abstract：

For many years, in the field of magnetic nanostructures we witness a strong interaction between experiment and first-principles theory. With the recent understanding of the relevance of the Dzyaloshinskii-Moriya (DM) interaction in ultrathin films deposited on metal surfaces [1], a new chapter in the field of research of low-dimensional magnetism was initiated. Appling first-principles calculations based on the density functional theory to ultrathin magnetic films, we explored the Dzyaloshinskii-Moriya interaction caused by spin-polarized electrons in the structure inversion asymmetric environment of 3d metal films on W substrates. We found that due to the large spinorbit interaction of the W substrate the Dzyaloshinskii interaction exceeds a critical strength and competes with the exchange interaction and causes the formation of one-dimensional short-period cycloidal magnetic spirals of unique winding sense in the Mn film [1, 2]. The phenomenon is more general than expected and was also found for finite magnetic wires of Fe-double chains grown in troughs of the reconstructed Ir(100)5x1 substrates [3]. Also the effect of the Dzyaloshinskii-Moriya interaction on the domain-walls will be discussed [4]. Recently we could go one step further and theoretically design a magnetic film, a monolayer of Fe on Ir(111) that exhibits a lattice of nontrivial two-dimensional magnetic structures, a nano-Skyrmion lattice [5]. We explore the phase diagram of the magnetic system based on parameters obtained from first-principles and finite size effects e.g. finite Fe clusters on Ir(111).

Acknowledgement:

This work was carried out in collaboration with Marcus Heide, Samir Lounis, Bernd Schweflinghaus, Bernd Zimmermann, Gustav Bihlmayer, Betrand Dupe, Stefan Heinze from the theory side and Matthias Bode, Matthias Menzel, Andre Kubetzka and Kirsten von Bergmann of the Wiesendanger group from the experimental side.

[1] M. Bode, M. Heide, K. von Bergmann, S. Heinze, G. Bihlmayer, A. Kubetzka, O. Piet-zsch, S. Blügel, R. Wiesendanger, Nature 447, 190 (2007).
[2] P. Ferriani, K. von Bergmann, E.Y. Vedmedenko, S. Heinze, M. Bode, M. Heide, G. Bihlmayer, A. Kubetzka, S. Blügel, R. Wiesendanger, Phys. Rev. Lett. 101, 027201 (2008).
[3] M. Menzel, Y. Mokrousov, R. Wieser, J. E. Bickel, E. Vedmedenko, S. Blügel, S. Heinze, K. von Bergmann, A. Kubetzka, and R. Wiesendanger, Phys. Rev. Lett. 108, 197204 (2012).
[4] M. Heide, G. Bihlmayer, and S. Blügel, Phys. Rev. B 78, 140403 (R) (2008); and Physica B 404, 2678 (2009).
[5] S. Heinze, K. von Bergmann, M. Menzel, J. Brede, A. Kubetzka, R. Wiesendanger, G. Bihlmayer, and S. Blügel, Nature Physics 7, 713 (2011).