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Berlin 2012 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 9: Poster I - Biomagnetism, FePt Nanoparticles, Magnetic Particles/Clusters, Magnetic Materials, Magnetic Semiconductors, Half-metals/Oxides, Multiferroics, Topological Insulators, Spin structures/Phase transitions, Electron theory/Computational micromagnetics, Magnetic coupling phenomena/Exchange bias, Spin-dependent transport, Spin injection/spin currents, Magnetization/Demagnetization dynamics, Magnetic measurement techniques

DF 9.32: Poster

Tuesday, March 27, 2012, 12:15–15:15, Poster A

Microscopic and macroscopic studies on the magnetoelectric coupling in chiral multiferroicsMax Baum1, •Jonas Stein1, Simon Holbein1, Thomas Finger1, Navid Qureshi1, Jeannis Leist3, Joachim Hemberger1, Petra Becker-Bohatý2, Ladislav Bohatý2, Götz Eckold3, and Markus Braden11II. Physikalisches Institut, Universität zu Köln — 2Institut für Kristallographie, Universität zu Köln — 3Institut für Physikalische Chemie, Universität Göttingen

In the chiral magnets MnWO4 and TbMnO3 ferroelectric polarisation is directly induced by the non-collinear magnetic structure. We present microscopic neutron scattering studies and macroscopic measurements of the ferroelectric polarisation and of the magnetic structure in these materials. Using a stroboscopic method the control of the chiral magnetism by an external electric field is analysed with polarised neutrons finding unexpectedly large relaxation times. Measurements of the pyrocurrent on MnWO4 confirm these long time scales. In addition we discuss the magnetic excitations at the incommensurate zone centre of MnWO4, a low energy mode should posses electromagnon character. The magnetic structure of NaFe(WO4)2 was studied by neutron diffraction. At zero magnetic field we find an incommensurate structure which transforms to commensurate order upon the application of moderate fields.

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