Abstract
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.
Highlights
Correlated materials with multiple order parameters provide unique insights into the fundamental interactions in condensed matter systems and present opportunities for innovative technological applications
The emergence of novel cross-coupling effects generated by multiple order parameters in a wide range of materials has provided new perspectives into the interactions that occur in condensed matter systems[1,2]
The antiferromagnet of C o4Nb2O9 has recently been in focus for its linear magnetoelectric behavior6,7,20–22. Co4Nb2O9 crystallizes in a trigonal P3c1 structure with two different types of honeycomb layers stacked alternately along the c axis
Summary
Correlated materials with multiple order parameters provide unique insights into the fundamental interactions in condensed matter systems and present opportunities for innovative technological applications. It has been believed that below TN, the ferroelectric polarization in CTO increases monotonously under increasing applied magnetic fields, similar to that in C o4Nb2O920–22 These studies were performed only on polycrystalline samples, in which the physical properties are averaged out over all spatial directions due to a large number of grains of varying orientations. Lattices, similar to the magnetic structure of C o4Nb2O921, the single crystalline CTO reveals strongly nonlinear magnetoelectric effect which is unique among A4B2O9 (A = Co, Fe, Mn and B = Nb, Ta) compounds[20,30,33,34,35,36] This suggests the existence of two different polarization components originating from inequivalent C o2+ sublattices. Our nontrivial discovery calls for further experimental and theoretical studies to reveal the underlying microscopic mechanism
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