Dynamics of skyrmions in magnets and a memory effect

Session Information

Location: amf. P7 | "Gheorghe Asachi" Technical University of Iași (TUIAȘI)
Day: 4. Thursday 18
Time: 09:00-10:00
Chairperson: Michele Ruggeri

Presentation Details

Presentation Type: Oral presentation
Title: Dynamics of skyrmions in magnets and a memory effect
Abstract: Topological solitons, such as skyrmion, in ferromagnets are known to be spontaneously pinned in the absence of an external force. When subjected to a force, such as a magnetic field gradient, they are deflected perpendicular to the applied force, resulting in dynamics that differ fundamentally from those of Newtonian particles. This behaviour is captured by the special conservation laws associated with linear momentum in ferromagnets. In antiferromagnets, by contrast, solitons can propagate freely in the absence of external forces and follow Newtonian and relativistic dynamics. We find that chiral skyrmions increase in size as their velocity increases, in contrast to the behaviour expected in Lorentz-invariant models. Skyrmions in synthetic antiferromagnets (two antiferromagnetically coupled ferromagnetic layers) initially behave similarly to ferromagnetic skyrmions under a magnetic field gradient, that is, the skyrmions in both layers move almost perpendicular to the field gradient. However, this motion is eventually halted leaving the two skyrmions separated by a finite distance. We find numerically that, below a critical magnetic field gradient strength, the system displays an unusual ”memory” effect: when the magnetic field gradient is removed, the skyrmions return to their original positions with high accuracy. We explain this phenomenon using a moduli-space approximation for the dynamics. Furthermore, we provide an exact treatment of the dynamics, demonstrating that small deviations from perfect positional memory can occur.

Presenter

Prof Stavros Komineas
University of Crete | Greece

Authors

1. Komineas, Stavros | Department of Mathematics and Applied Mathematics, University of Crete, 70013 Heraklion, Greece
2. Barton-Singer, Bruno | Institute of Applied and Computational Mathematics, Foundation for Research and Technology, 70013 Heraklion, Greece
3. Navallur, Anusree | Department of Mathematics and Applied Mathematics, University of Crete, 70013 Heraklion, Greece