Origin of forbidden reflections in multiferroic Ba2CoGe2O7by neutron diffraction: symmetry lowering or Renninger effect? Article Swipe
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· 2016
· Open Access
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· DOI: https://doi.org/10.1107/s1600576716002405
· OA: W2963141212
For a symmetry-consistent theoretical description of the multiferroic phase of Ba 2 CoGe 2 O 7 a precise knowledge of its crystal structure is a prerequisite. In a previous synchrotron X-ray diffraction experiment on multiferroic Ba 2 CoGe 2 O 7 at room temperature, forbidden reflections were found that favour the tetragonal-to-orthorhombic symmetry lowering of the compound [Hutanu, Sazonov, Murakawa, Tokura, Náfrádi & Chernyshov (2011), Phys. Rev. B , 84 , 212101]. Here, the results are reported of room-temperature single-crystal diffraction studies with both hot and cold neutrons to differentiate between genuine symmetry lowering and multiple diffraction (the Renninger effect). A comparison of the experimental multiple diffraction patterns with simulated ones rules out symmetry lowering. Thus, the structural model based on the tetragonal space group P\overline{4}2_{1}m was selected to describe the Ba 2 CoGe 2 O 7 symmetry at room temperature. The precise structural parameters from neutron diffraction at 300 K are presented and compared with the previous X-ray diffraction results.
