Regensburg 2010 – scientific programme
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DF: Fachverband Dielektrische Festkörper
DF 4: Multiferroics I (Joint Session of MA, DF, KR, DS)
DF 4.8: Talk
Monday, March 22, 2010, 12:15–12:30, H3
Neutron scattering studies on chiral multiferroics: magnetic structure and excitations — •T. Finger1, M. Baum1, A. C. Komarek1, D. Senff1, P. Link6, K. Hradil5, K. Schmalzl4, W. Schmidt4, L.-P. Regnault3, D. N. Argyriou7, P. Becker-Bohaty2, L. Bohaty2, and M. Braden1 — 1II. Physikalisches Institut, Universität zu Köln — 2Institut für Kristallographie, Universität zu Köln — 3CNG-Grenoble / ILL, Grenoble — 4FZ Jülich, JCNS at ILL, Grenoble — 5Universität Göttingen / FRM2 München — 6FRM2, TU München, München — 7HMI, Berlin
We present neutron-scattering experiments on IN12 and on IN14 using spherical polarization analysis directly documenting the poling of the elastic magnetic chiral terms for the spiral magnets MnWO4 and TbMnO3 by cooling in an electric field. In addition, we were able to observe a multiferroic hysteresis curve as function of electric field in both compounds and succeeded to switch the spiral at constant temperature, which is the central issue in view of future applications. Additionally, measurements of the diffuse scattering slightly above the multiferroic transition show some small chiral terms remaining in the collinear phase. The close coupling of ferroelectricity and magnetism in the multiferroic materials also results in new collective excitations, predicted almost 20 years ago: hybridised spin-phonon excitations, referred to as "electromagnons". After the first observations of potential electromagnon modes in infra-red and in neutron studies a conclusive interpretation is still missing. Our most recent neutron scattering measurements will be discussed.