Electric polarization reversal and nonlinear magnetoelectric coupling in the honeycomb antiferromagnet Fe4Nb2O9 single crystal

As a new magnetoelectric material, honeycomb-based antiferromagnet Fe4Nb2O9 has attracted a great deal of attention due to its prominent magnetoelectric (ME) coupling and high Neel temperature, while the physics of magnetoelectricity is far from understood. In the present study, we present our systematic investigations of the anisotropic ME effect, electric polarization reversal, and nonlinear ME effect of Fe4Nb2O9 single crystals, thus highlighting the phase diagram extended down to 10 K. Our results provide clear evidence for electric polarization reversal driven by magnetic field (H) along the [110] and [1-10] directions, respectively, while no such polarization reversal occurs as His applied along the [001] direction. The nonlinear ME effects and electric control of magnetism are unambiguously demonstrated. In addition, the angular-dependent probing reveals a 2 theta rotation of the induced electric polarization around the c axis upon the rotation of magnetic field by an angle theta. The electric polarization responses and concomitant ME coupling are well explained by means of the metal-ligand hybridization p -d mechanism. This work represents an essential step forward in the understanding of ME coupling not only in this A4M2O9 honeycomb magnet.

Automated summary

In this study, the anisotropic magnetoelectric effect, electric polarization reversal, and nonlinear magnetoelectric effect of the honeycomb-based antiferromagnet Fe4Nb2O9 were systematically investigated. The phase diagram was extended down to 10 K. It was found that electric polarization reversal occurred when the magnetic field was applied along the [110] and [1-10] directions, but not along the [001] direction. Angular-dependent probing revealed a rotation of the induced electric polarization around the c axis upon the rotation of magnetic field. The electric polarization responses and magnetoelectric coupling were explained by the metal-ligand hybridization mechanism. This work is important for understanding magnetoelectric coupling in A4M2O9 honeycomb magnets.