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MA: Fachverband Magnetismus

MA 20: Multiferroics

MA 20.8: Vortrag

Mittwoch, 27. Februar 2008, 15:45–16:00, EB 202

Spindynamics of multiferroic HoMnO₃ — •Tim Hoffmann¹, Tim Günter¹, Takuya Satoh², Thomas Lottermoser¹, and Manfred Fiebig¹ — ¹HISKP, Universität Bonn, Nussallee 14-16, 53115 Bonn, Germany — ²Department of Basic Science, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan

HoMnO₃ is a promising multiferroic because of the unusually pronounced coupling of electric and magnetic order manifesting as giant magnetoelectric effect. Static measurements have shown that the mangetic state of the Ho spins can be controlled by an external electric field [1]. We have investigated the dynamical properties of the magnetoelectric coupling of hexagonal HoMnO₃ using optical pump-probe experiments with 130 fs time resolution. Around 37 K a reorientation of the Mn spins is induced by competition of Ho-order, Mn-order and ferroelectric distortion, thus reflecting the multiferroic coupling. The reorientation is triggered by a pump pulse at 1.55 eV and probed time-resolved by optical second harmonic generation. Results point to an optically induced reorientation of Mn spins within a few hundreds of picoseconds. Is is superimposed by an oscillation with a 10 ns period around the new orientation. Possible explanations of these effects will be discussed.

[1] T. Lottermoser et al., Nature 430, 541 (2004)