Berlin 2012 – scientific programme

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DS: Fachverband Dünne Schichten

DS 19: Poster I: Multiferroics (jointly with MA, DF, KR, TT), Spins in organic materials (jointly with MA), FePt Nanoparticles (jointly with MA, MM)

DS 19.32: Poster

Tuesday, March 27, 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.