Regensburg 2013 – scientific programme

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AGjDPG: Arbeitsgruppe junge DPG

AGjDPG 2: Topological Defects in Magnetic Materials: from Devices to Cosmos
(PhD-Student Symposium jointly with MA)

AGjDPG 2.7: Talk

Tuesday, March 12, 2013, 12:15–12:30, H16

Ferroelectric Vortices in Hexagonal YMnO₃ — •Martin Lilienblum — Department of Materials, ETH Zurich

Hexagonal rare earth manganites RMnO₃ (R= Sc, Y, Dy-Lu) exhibit an intriguing domain structure with kaleidoscopic intersections of always six individual domains. These ferroelectric vortices can be seen as topological defects that forms while cooling across the ferroelectric phase transition. Topological defect formation is of general interest since, for example, topological defects may have played an important role during the evolution of the early universe. Here we present an experimental study on the stability of the ferroelectric vortices in flux grown YMnO₃ single crystals in annealing experiments up to the phase transition temperature of around 1300 K. In a second experiment we studied the dependence of the density of ferroelectric vortices on the cooling rate. In order to ensure the visualization of the true bulk domain structure we performed an elaborate sample processing by annealing, polishing and piezoresponse force microscopy. In a third experiment we studied the progression of the ferroelectric order parameter below the phase transition by optical second harmonic generation.