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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 11: Ferroics - Domains and Domain Walls (joint session KFM/MA)

KFM 11.1: Vortrag

Mittwoch, 18. März 2020, 15:00–15:20, TOE 317

Ferroelectric Domain Structure In Hexagonal Yttrium Manganite Thin Films - A Phase Field Study — •Amadé Bortis, Manfred Fiebig, and Thomas Lottermoser — Department of Materials, ETH Zurich, Zurich, Switzerland

The topologically protected vortex domains in hexagonal rare-earth manganites exhibit rich physics, both from a fundamental and application point of view. In thin films, however, the nanoscale domain size has thus far hindered the experimental investigation of domain patterns - the existence of vortex domains remains elusive. Here, we use a phase-field model based on a known Landau expansion of the free energy and incorporate boundary conditions for a thin film. With this model, we investigate up to which thickness a thin films retains the bulk-like vortex-string network - closed loops of connected vortices. We simulate the evolution of the structural domains for different thicknesses. In the ultrathin regime, we find straight lines of vortices emerging perpendicular to the films surface, similar to stacked 2D vortex patterns. As the thickness increases, we find an intermediate regime where the vortex lines start bending and merging, while still not being connected into closed loops. Finally, the bulk-like vortex-strings are recovered for a thickness of about 50 unit cells. Our work shows an effective 2D to 3D transition in rare-earth manganite thin films, revealing the impact of confined dimensionality on the domain topology.