Regensburg 2019 – scientific programme

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SYSD: Symposium SKM Dissertation-Prize 2019

SYSD 1: SKM Dissertation Prize

SYSD 1.7: Invited Talk

Monday, April 1, 2019, 11:30–11:50, H2

Helimagnets, sand patterns and fingerprints linked by topology — •Peggy Schönherr — ETH Zürich, Zürich, Switzerland

Helimagnets, liquid crystals, sand patterns, and fingerprints are examples of lamellar materials with periodically assembled layers. The lamellar texture imparts a unique combination of order and mobility finding, having profound implications in biology, physics, chemistry, and technology. They also find applications in liquid-crystal displays and electro-optical devices. Order and mobility are strongly affected by the presence of topological defects arising from imperfections in the planar configuration. In my talk, I will demonstrate that helimagnets are a striking analogue to liquid crystals showing similar ordered topological defects that are typical for lamellar materials like sand patterns or fingerprints. Crucially, however, the topological structures exist at the nanoscale with additional functionality arising from the magnetic order. Combining magnetic force microscopy and micromagnetic simulations, I will show three fundamental classes of domain walls to arise in the near-room-temperature helimagnet iron germanium. In contrast to conventional ferroics, the domain walls exhibit a well-defined inner structure, which - analogous to cholesteric liquid crystals - consists of topological disclination and dislocation defects. Similar to the magnetic skyrmions, such domain walls can carry a finite topological charge, permitting an efficient coupling to spin currents and contributions to a topological Hall effect, opening the door to innovative device concepts.