3D Magnetic Textures with Mixed Topology

Date

Nov 10, 2025

Time

2:00 PM - 3:00 PM

Speaker

Dr. Maria Azhar

Affiliation

Faculty of Physics and CENIDE, University of Duisburg-Essen

Language

en

Main Topic

Materialien

Host

Grit Rötzer

Description

Magnetic materials can host complex spin textures stabilized by the interplay of competing interactions. When these textures are topologically protected, they gain robustness against perturbations. In this talk, I will introduce a range of such configurations—including spin spirals, vortices, skyrmions, hopfions, multi-q states, and recently discovered screw dislocation defects [1]—and explain their stability from a topological perspective. In 3-dimensional systems, topology plays an even richer role, enabling knotted and linked structures like hopfions [2] that are characterised by an integer Hopf index H. However, traditional classifications using homotopy groups fall short when magnetic textures form in non-uniform backgrounds. I will present a new framework [3] based on flux tubes of emergent magnetic field, and their linking numbers, culminating in an analytical formula for the Hopf index H as a flux-weighted average of these linking numbers. This approach not only enables efficient computation of H in finite systems—avoiding the difficulties associated with numerical evaluation of the Whitehead integral [4]—but also reveals that non-integer or continuously varying H can emerge in "mixed topology" states. Such textures interpolate between distinct topological sectors, providing new insight into the topology and tunability of magnetic textures. References [1] M. Azhar et al., Phys. Rev. Lett., 2022, 128, 157204. [2] Faddeev, L., Niemi, Nature, 1997, 387, 58–61; P. Sutcliffe, Phys. Rev. Lett., 2017, 118, 247203. [3] M. Azhar et al., 2024, arXiv:2411.06929. [4] R. Knapman, M. Azhar, et al., Phys. Rev. B., 2024, 111, 134408. .

Links

• Seminars at the IFW

Last modified: Nov 10, 2025, 7:38:17 AM