Regensburg 2010 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 5: Multiferroics II (Joint Session of MA, DF, KR, DS)

DF 5.1: Vortrag

Montag, 22. März 2010, 14:00–14:15, H3

Switching of a spin-spiral-induced polarization in multiferroic MnWO₄ — •Tim Hoffmann¹, Dennis Meier¹, Petra Becker-Bohatý², Ladislav Bohatý², and Manfred Fiebig¹ — ¹HISKP, Universität Bonn — ²Institut für Kristallographie, Universität zu Köln

Coexisting ferroic orders become interesting when there is an interaction between them. Especially applying an electric field and thus changing the magnetic order is highly desirable for possible applications. In spite of the declared interest in multiferroics to switch a magnetization by an electric field nothing is known about the dynamics of the actual switching process.

The coupling of ferroelectric and magnetic order is intrinsically strong in spin-spiral multiferroics, where ferroelectricity emerges as a consequence of complex magnetic long-range order. Here we observe the manipulation of magnetically-induced ferroelectric domains in MnWO₄ by optical second harmonic generation (SHG). Application of an electric field allows to transform the sample to an electric as well as magnetic single-domain state. Moreover we obtained images of the domain structures during the transition revealing the growth of the domains. When cooled in zero-field, the domains have a bubble-like topology. Interestingly, after recovery from a single domain state the shape changes to a stripe structure and the domain size is significantly increased. Effects of the shape and duration of the electric-field poling pulses are investigated. Furthermore, in contrast to typical ionic ferroelectrics the spontaneous polarization can be switched without fatigue – no defects or pinning effects constrain the movement of domain walls.