Current-Driven Dynamics of Magnetic Skyrmions in Low Pinning Multilayer Structures at Room Temperature
Kai Litzius (Institut für Physik)

Magnetic skyrmions [1,2] are nanoscale magnetic quasi-particles whose spin structure can be mapped continuously on a sphere. They are promising candidates for future spintronic devices such as the skyrmion racetrack memory. [3] Skyrmions have been first predicted in bulk magnetic materials due to the Dzyaloshinskii-Moriya interaction (DMI) that favors a chiral spin canting. [4,5] Within the last years, DMI was also reported in different thin films due to broken inversion symmetry at the interfaces.
Additionally, these films can exhibit a significant spin Hall effect that leads to efficient spin dynamics, making thin film systems extremely promising for skyrmion dynamics. [6] Recently, the possibility to move skyrmions efficiently in applications’ relevant geometries and at reasonable current densities was reported. [7] However, to understand the dynamics of skyrmions, it is critical to investigate the real-time behavior of skyrmions when excited by current pulses.
In this work, we report the time-resolved pump-probe observation of magnetic skyrmion dynamics at room temperature in thin film devices by scanning transmission X-ray microscopy. Our findings reveal fully reproducible motion due to spin orbit torques and skyrmion velocities close to the ideal micromagnetic predictions, as required for any future application. Furthermore, we find indications that the usually assumed rigid skyrmion model has to be extended to describe all dynamic properties of the skyrmions correctly.

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