Skyrmion Dynamics under the Influence of Defects from DFT to ASD

Any potential skyrmionic application must be able to handle the impact of defects on the skyrmion motion. Until now, most approaches focus on large skyrmions using phenomenological schemes in the micromagnetic regime. Using a combination of first-principles calculations and atomistic spin dynamics, the complex motion of technologically more relevant small skyrmions in Pd/Fe/Ir(111) with 3d and 4d single-atomic defects is studied. Recently, it was shown that such defects can either repel or pin skyrmions [1]. It can be observed that the current threshold needed to overcome the energy barriers, resulting from the impurities, depends on their chemical nature. The obtained dynamical behaviour is richer and goes beyond the expected from the Thiele equation. The complexity of the different motion regimes is revealed and compared with what is known for larger skyrmions. The present study also shines light on how one can engineer defects-based pathways for controlled skyrmion motion.
[1] Lima Fernandes I. et al., Nat. Commun. 9, 4395 (2018).