Berlin 2015 – scientific programme

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MA: Fachverband Magnetismus

MA 22: Multiferroics I (DF with DS/KR/MA/TT)

MA 22.8: Talk

Wednesday, March 18, 2015, 11:30–11:45, EB 107

Emergence of ferroelectricity in multiferroic h-YMnO₃ — •Martin Lilienblum¹, Thomas Lottermoser¹, Sebastian Manz¹, Sverre M. Selbach², Andres Cano³ und Manfred Fiebig¹ — ¹Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 4, 8093 Zurich, Switzerland — ²Department of Material Science and Engineering, NTNU, N-7491 Trondheim, Norway — ³CNRS, Université de Bordeaux, ICMCB, UPR 9048, F-33600 Pessac, France

Universal scaling laws, interfacial nano-electronics, and topological defects are currently studied using hexagonal manganites RMnO₃ (R= Sc, Y, Dy-Lu) as model system. In spite of the remarkably broad interest in the system, surprisingly little is known about the origin of the ferroelectric state. Here we solve the controversy about the emergence of the spontaneous polarization and its coupling to the underlying structural distortion by applying scanning probe microscopy (SPM) and optical second harmonic generation (SHG). We trace the spontaneous polarization by SHG from 100 K to 1450 K directly and contact-free. We find that only a single transition exists in which the polarization arises slower than expected as by-product of the structural distortion. By thermal treatments close to the structural transition and subsequent SPM scans, we show that the exceptionally robust ferroelectric domain pattern is determined only by the structural distortion. In summary we reveal that the ferroelectric order results from an interplay of electric polarization, topological effects, and temperature.