In a collaboration with colleagues at Johannes Gutenberg-Universität Mainz, Uppsala Universitet, and Christian-Albrechts-Universität zu Kiel, we have shown theoretically that skyrmions and antiskyrmions can behave very differently under spin-orbit torques. One key finding is that antiskyrmions can undergo trochoidal motion, which is analogous to Walker breakdown in domain wall dynamics. This threshold defines a speed limit for rectilinear displacement. Another is the onset of skrymion-antiskyrmion pair generation under large damping-like torques, which results in a gas with excess skyrmions. This imbalance in matter-antimatter production is a consequence of the asymmetric dynamics at high energies.
This work recently appeared in Nature Electronics.
— Phys.org (@physorg_com) August 15, 2018
"we naturally assumed that the kinematics of antiskyrmions could be described by simply changing the sign of the topological charge in the Thiele equation, but we have found that things aren’t as simple as this” https://t.co/vN7UePMhw5 #skyrmion pic.twitter.com/18OA7DFLzq
— Physics World (@PhysicsWorld) August 24, 2018
We studied how current-driven skyrmion motion in ultrathin films is affected by disorder. We modelled the disorder by assuming a grain structure, where the local perpendicular anisotropy fluctuates from grain to grain. We find that the velocity versus current curves are reminiscent of behavior in driven elastic interfaces in disordered media, such as domain wall creep. Moreover, we identify an extrinsic contribution to the skyrmion Hall effect due to disorder scattering, which is drive dependent. This work has just appeared in Applied Physics Letters.
We show how inhomogeneous spin polarizers in the form of vortices can result in self-sustained gyration of skyrmions in magnetic nanopillars. We suggest that such dynamics could be useful for skyrmion-based spin-torque nano-oscillators. This work has just appeared in the New Journal of Physics.
Our European project MAGicSKy on magnetic skyrmions is well underway with project leaders and participants from the consortium gathering in Massy this week for the inaugural project meeting.
This FET-Open project is funded by the Horizon2020 Framework Programme of the European Union and will run through to September 2018.