Strongly correlated materials with multiple order parameters provide unique insights into the fundamental interactions in condensed matter systems and present opportunities for innovative technological applications. A class of antiferromagnetic honeycomb lattices compounds, A4B2O9 (A = Co, Fe, Mn; B = Nb, Ta), have been explored owing to the occurrence of linear magnetoelectricity. From our investigation of magnetoelectricity on single crystalline Co4Ta2O9, we discovered strongly nonlinear and antisymmetric magnetoelectric behavior above the spin-flop transition for magnetic fields applied along two orthogonal in-plane directions. This observation suggests that two types of inequivalent Co2+ sublattices generate magnetic-field-dependent ferroelectric polarization with opposite signs. The results motivate fundamental and applied research on the intriguing magnetoelectric characteristics of these buckled-honeycomb lattice materials.
Bibliographical noteFunding Information:
The work at Yonsei was supported by the National Research Foundation of Korea (NRF) Grants (NRF-2017R1A5A1014862 (SRC program: vdWMRC center), NRF-2018R1C1B6006859, and NRF-2019R1A2C2002601). VK and SC were supported by the NSF, Grant No DMR-1609935. SC was also supported by the international postdoctoral scholarship at Max Planck Institute for Solid State Research, Stuttgart, Germany. The authors are grateful to Prof. G. Schütz for supporting AC measurements with the MPMS magnetometry.
© 2020, The Author(s).
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