Dresden 2020 – scientific programme

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MA: Fachverband Magnetismus

MA 47: Skyrmions IV (joint session MA/TT)

MA 47.7: Talk

Thursday, March 19, 2020, 11:00–11:15, POT 6

Hopfions in magnetic crystals — Filipp N. Rybakov¹, •Nikolai S. Kiselev², Aleksandr B. Borisov³, Lukas Döring⁴, Christof Melcher⁴, and Stefan Blügel² — ¹Department of Physics, KTH-Royal Institute of Technology, SE-10691 Stockholm, Sweden — ²Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, 52425 Jülich, Germany — ³Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, Ekaterinburg 620990, Russia — ⁴Department of Mathematics I & JARA FIT, RWTH Aachen University, 52056 Aachen, Germany

Hopfions are three-dimensional topological solitons, which can be thought of as skyrmion tubes with closed ends. In the pioneering work of Bogolyubsky [1], it was shown that in the micromagnetic model with higher-order derivatives of the order parameter, the hopfions might appear as statically stable solutions. Here we show that the general form of such a micromagnetic functional can be derived from classical spin-lattice Hamiltonians with competing Heisenberg exchange interactions. We present this advanced micromagnetic functional derived for lattices of cubic symmetry and provide a criterion for the existence of hopfions in the systems described by such a functional [2]. Following our approach, similar functionals can be derived for materials of any crystal symmetry. We discuss a variety of hopfion solutions, their static and dynamic properties, and provide concrete guidance for the search of magnetic crystals that allow the existence of hopfions.
[1] I. L. Bogolubsky, Phys. Lett. A 126, 511 (1988).
[2] F. N. Rybakov, et al., arXiv:1904.00250.