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Magnetismus Poster: Do., 13:00–15:30 D-P219
Investigation of multiferroic TbMnO3 and DyMnO3 in high magnetic fields
Britta Bohnenbuck 1 , Jörg Strempfer 1 , Ioannis Zegkinoglou 1 , Nadir
Aliouane 2 , Dimitri N. Argyriou 2 , Sven Landsgesell 2 , Martin v.
Zimmermann 3
1 Max-Planck-Institut für Festkörperforschung, Heißenbergstraße 1, 70569 Stuttgart –
2 Hahn-Meitner-Institut, Glienicker Straße 100, 14109 Berlin – 3 HASYLAB, Notkestra-
ße 85, 22603 Hamburg
TbMnO3 and DyMnO3 are improper ferroelectrics with a spontaneous polarization occurring
below 28K and 18K, respectively. Both exhibit a polarization flop from P || c to
P || a in an applied magnetic field. In order to study the interplay between magnetism,
lattice distortions, and polarization we investigated the temperature and magnetic
field dependence of structural superstructure reflections at the positions (0 δm l) and
(0 2δm l) using x-ray diffraction. At zero field only second order superstructure reflections
are observed whereas first order superstructure reflections appear in an applied
magnetic field which increase linearly in intensity with magnetic field. This indicates
that the quadratic magneto-elastic coupling breaks down in a magnetic field and a
linear coupling is induced. In TbMnO3, the polarization flop from P || c to P || a
coincides with an incommensurate (IC) to commensurate (C) transition of the wave
vector. This is not the case for DyMnO3, where no wave vector change is observed at
the critical magnetic field. The role of the IC to C phase transition will be discussed
with respect to the polarization flop.