Magnetic skyrmions: investigation and manipulation by STM
Dr. Kirsten von Bergmann (Universität Hamburg)

Magnetic skyrmions are topologically distinct from their ferromagnetic environment.
They may form in an inversion asymmetric environment and are induced by a competition between magnetic exchange, Dzyaloshinsky-Moriya interaction, and typically the Zeeman energy. Scanning tunneling microscopy (STM) is a valuable tool to study the properties of nanometer-scale skyrmions [1]. In addition to measurements with spin-polarized STM tips skyrmions can also be detected with unpolarized electrodes due to spin-mixing effects in the non-collinear spin texture.
We employ spatially resolved magnetic field dependent tunneling spectroscopy to identify this effect of non-collinear magnetoresistance and find that it scales with the angle between nearest neighbors [2]. With a nonmagnetic STM tip it is also possible to locally switch the topology of a thin magnetic layer via the sign of the electric field between tip and sample [3]. The combination of these two phenomena –electrical detection and electric field switching of topologically distinct states– could lead to a robust non-magnetic read- and write-head for future skyrmion racetracktype devices.
[1] K. von Bergmann et al., J. Phys.: Cond. Mat. 26, 394002 (2014).
[2] C. Hanneken et al., Nature Nanotechn. 10, 1039 (2015).
[3] P.-J. Hsu et al., arXiv:1601.02935.