Berlin 2015 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 4: Focused Session on Ferroic Domain Walls I (DF with MA)
DF 4.2: Vortrag
Montag, 16. März 2015, 15:30–15:50, EB 107
Dielectric properties of multiferroic hexagonal manganites — •Stephan Krohns1, Eugen Ruff1, Peter Lunkenheimer1, Martin Lilienblum2, Dennis Meier2, Manfred Fiebig2, and Alois Loidl1 — 1Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Germany — 2Multifunctional Ferroics, Department of Materials, ETH Zurich, Switzerland
Hexagonal manganites exhibit a broad variety of highly interesting features as, e.g., domain-wall structure, geometric improper ferroelectricity and antiferromagnetic ordering. The exact mechanism for ferroelectricity is still under debate as well as the impact of the domain-wall structure to macroscopic quantities (e.g., the dielectric constant). A technique to determine the multiferroic, ferroelectric and domain-wall polarisation phenomena is the measurement of the dielectric response to ac and dc electric fields. Here we thoroughly analyse the dielectric response of YMnO3 single crystals in a broad temperature and frequency range. The crystals were subjected to precisely defined cooling rates from above the ferroelectric transition to vary their domain-wall densities. Two relaxation processes occur at temperatures below 350 K. The major one points to an extrinsic so-called Maxwell-Wagner relaxation, based on a thin insulating layer at the surface of the sample. The second, smaller relaxation seems to be of intrinsic origin. We address the question if the macroscopic dielectric properties are influenced by the ferroelectric domain-wall structure.