Remarkable magnetoelectric effect in single crystals of honeycomb magnet Mn4Nb2O9

Linear magnetoelectrics refer to those compounds in which ferroelectric (FE) polarization can be generated by applying the magnetic field. This scenario opens an additional avenue toward high-temperature magnetoelectric (ME) coupling that is achievable in a large class of relatively weak frustrated magnetic systems such as honeycomb antiferromagnets. It is, thus, urgent to unveil the physics underlying the linear ME coupling in these linear ME materials. We grow the single crystals of Mn4Nb2O9, a linear ME candidate with high magnetic ordering temperature, and carry out a set of structural, magnetic, and ME characterizations. An antiferromagnetic ordering with [001]-oriented moments at the Neel point T-N=109K is identified together with magnetic field driven large electric polarization emerging at T-N, due to the strong exchange striction dependent mechanism. The measured ME coupling tensor alpha fits well the magnetic symmetry -3 ' m ', consistent with the linear ME scenario. Furthermore, remarkable responses of FE polarization and magnetization to the magnetic field and electric field, respectively, are demonstrated.