Noncollinear antiferromagnetic order in the buckled honeycomb lattice of magnetoelectric Co4Ta2O9 determined by single-crystal neutron diffraction

ORAL

Abstract

Co4Ta2O9 is a newly interested magnetoelectric material with strong coupling. It exhibits unusual magnetoelectric effects, including sign change and non-linearity, which cannot be understood without detailed knowledge of the magnetic structure.

Here, we report systematic neutron diffraction measurements and direction-dependent magnetic susceptibility measurements on Co4Ta2O9 single crystals [1]. Below 20.3 K, we find a long-range antiferromagnetic order in the alternating buckled and flat honeycomb layers of Co2+ ions stacked along the c-axis. Within experimental accuracy, we propose the magnetic moments lying in the ab-plane as a minimal model. They form a tilted antiferromagnetic structure with a tilt angle of about 14 degrees at 15 K in each buckled layer and collinear moments in each flat layer, directly evidenced by a finite (0, 0, 3) magnetic Bragg peak. The obtained magnetic space group is C2'/c, different from C2/c' previously reported by powder neutron diffraction and in the isostructural Co4Nb2O9. Our revised magnetic structure successfully explains the main features of the magnetoelectric tensor of Co4Ta2O9 within the framework of the spin-flop model.

[1] Sungkyun Choi et al., https://arxiv.org/abs/2007.06561 (2020).

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Presenters

  • Sungkyun Choi

    • Rutgers University, New Brunswick
    • Department of Physics and Astronomy, Rutgers University

Authors

  • Sungkyun Choi

    • Rutgers University, New Brunswick
    • Department of Physics and Astronomy, Rutgers University

  • Donggun Oh

    • Yonsei University

  • Matthias Gutmann

    • Rutherford Appleton Laboratory
    • Rutherford Appleton Lab
    • STFC-Rutherford Appleton Laboratory, ISIS Facility
    • ISIS Facility, Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX, United Kingdom

  • Shangke Pan

    • Ningbo University

  • Gideok Kim

    • Max Planck Institute for Solid State Research

  • Kwanghyo Son

    • Max Planck Institute for Intelligent Systems
    • Department of Modern Magnetic Systems, Max Planck Institute for Intelligent Systems

  • Jae Wook Kim

    • Rutgers University, New Brunswick

  • Nara Lee

    • Yonsei University

  • Sang-Wook Cheong

    • Rutgers University, New Brunswick
    • Department of Physics and Astronomy, Rutgers University-New Brunswick
    • Rutgers Center for Emergent Materials, Rutgers University
    • Rutgers, The State University of New Jersey
    • Rutgers University
    • Department of Physics and Astronomy, Rutgers University
    • Center for Quantum Materials Synthesis, Rutgers University
    • Center for Emergent Materials and Department of Physics and Astronomy, Rutgers

  • Youngjai Choi

    • Yonsei University

  • Valery D Kiryukhin

    • Rutgers University, New Brunswick
    • Department of Physics and Astronomy, Rutgers University