Berlin 2018 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 12: Multiferroics and magnetoelectrics II (joint session MA/KFM)

KFM 12.7: Talk

Wednesday, March 14, 2018, 11:15–11:30, EB 202

Magnetic field control of cycloidal domains and electric polarization in multiferroic BiFeO₃ — •Sándor Bordács¹, Dániel Farkas¹, Jonathan White², Robert Cubitt³, Lisa DeBeer-Schmitt⁴, Toshimitsu Ito⁵, and István Kézsmárki^1,6 — ¹Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-optical Spectroscopy Research Group, Budapest, Hungary — ²Laboratory for Neutron Scattering and Imaging, PSI, Villigen, Switzerland — ³Institut Laue-Langevin, Grenoble, France — ⁴Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA — ⁵National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan — ⁶Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg, Germany

The magnetic field induced rearrangement of the cycloidal spin structure in ferroelectric monodomain single crystals of the room-temperature multiferroic BiFeO₃ is studied using small-angle neutron scattering (SANS). The cycloid propagation vectors are observed to rotate when magnetic fields applied perpendicular to the rhombohedral (polar) axis exceed a pinning threshold value of ∼5 T. In light of these experimental results, a phenomenological model is proposed that captures the rearrangement of the cycloidal domains, and we revisit the microscopic origin of the magnetoelectric effect. A new coupling between the magnetic anisotropy and the polarization is proposed that explains the recently discovered magnetoelectric polarization to the rhombohedral axis.