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MA: Fachverband Magnetismus

MA 44: Non-Skyrmionic Magnetic Textures

MA 44.5: Talk

Thursday, March 21, 2024, 16:15–16:30, EB 301

Screw dislocations and fractional hopfion rings in chiral magnets — •Maria Azhar — Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 47057 Duisburg, Germany

In chiral magnets, topological defects such as Skyrmions and Hopfions are typically considered in a ferromagnetic background. Recently we predicted that helical phases offer a plethora of novel topological spin textures including screw dislocations where the helical order locally arranges as a spiral staircase [1]. These new topological spin structures, which appear in many facets and look very different locally, have the remarkable property that their far field is universally determined by a topological index ν characterizing the dislocation. Intriguingly, we identify screw dislocations with a smooth magnetic core and a simple screw structure (ν = +1), that can be continuously deformed either to vortices of the XY-order parameter or to vortex strings encircled by fractional Hopfion rings. The latter prediction has recently been experimentally confirmed by means of transmission electron microscopy [2]. Another astonishing spin structure that we predicted arises from a singular core comprising a chain of Bloch points with alternating topological charge. Our findings enrich the portfolio of topological magnetic structures ubiquitously being present in bulk and thin-film helimagnets and will play a crucial role on the way to 3D nanomagnet and spintronics applications.

[1] M. Azhar, V. Kravchuk, and M. Garst, PRL 128, 157204 (2022)

[2] F. Zheng, et al. Nature 623, 718 (2023).

Keywords: Chiral magnets; Screw dislocations; helimagnets; skyrmions; hopfions