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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 3: Focus Session: (Multi-)Ferroic States I

KFM 3.2: Talk

Monday, March 18, 2024, 09:50–10:10, EMH 225

The three-dimensional multiferroic domain structure of hexagonal manganites — Lukas Heckendorn, •Aaron Merlin Müller, Manfred Fiebig, and Thomas Lottermoser — Department of Materials, ETH Zurich, 8093 Zurich, Switzerland

We simulate and visualize the three-dimensional domain structure and associated topological features of multiferroic hexagonal manganites. Due to the improper nature of their ferroelectric order, hexagonal manganites exhibit unconventional six-fold vortices in their ferroelectric domain patterns. In 3D, these domain patterns are characterized by vortex lines, which are 1D topological defects that form loops in bulk materials. Below the Néel temperature, an additional antiferromagnetic order rigidly coupled with the ferroelectric order emerges, forming vortex domain patterns of its own. In our simulations, we observe new types of antiferromagnetic three-fold, four-fold and six-fold vortex lines in addition to ferroelectric six-fold vortex lines. We relate the existence of these vortex lines to the rigid coupling between orders. Our numerical investigation is performed with a phase-field model to simulate the domain structure in three dimensions using a Landau-free-energy expansion.

Keywords: Multiferroics; Ferroelectrics; Antiferromagnets; Phase-Field Simulations; Time-Dependent Ginzburg-Landau