Probing the ground state magnetic structure of magnetic multiferroic Fe4Nb2O9

Fe4Nb2O9 is a magnetic multiferroic member in the family of honeycomb antiferromagnet A4B2O9. The polycrystalline sample shows another transition around 77 K apart from the antiferromagnetic transition at 90 K in the temperature dependent dielectric permittivity study. This second transition could be the signature for a spin reorientation or structural transition. However, the origin of the magnetoelectric coupling in this type of magnetic multiferroic is still to be explored. For this investigation, it is utmost important to find out the arrangement of magnetic spins with respect to the crystal structure and for this investigation, single-crystal neutron diffraction is the most suitable probe. Hence we are proposing here to perform single-crystal neutron diffraction on Fe4Nb2O9 crystal grown using floating zone technique.