Berlin 2012 – wissenschaftliches Programm

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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

Dienstag, 27. März 2012, 12:15–15:15, Poster A

Microscopic and macroscopic studies on the magnetoelectric coupling in chiral multiferroics — Max Baum¹, •Jonas Stein¹, Simon Holbein¹, Thomas Finger¹, Navid Qureshi¹, Jeannis Leist³, Joachim Hemberger¹, Petra Becker-Bohatý², Ladislav Bohatý², Götz Eckold³, and Markus Braden¹ — ¹II. 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.