Reliable determination of noncollinear magnetic order of Co4Nb2O9 to explain its nontrivial magnetoelectricity

Magnetic materials with strong spin-orbit interactions are drawing strong attention as candidates to realise novel functional properties. Magnetoelectricity (also named as multiferroicity) with strong spin-orbit-coupled magnetic ions attracts special attention as the magnetic frustration and anisotropy play a corporated role in realising the new mechanism for an intrinsic coupling between the magnetisation and electric polarisation. In this project, we focus on a honeycomb antiferromagnet magnetoelectricity with strong magnetoelastic coupling: Co4Nb2O9 with strong spin-orbit-coupled Co2+ ions. Our purpose is to determine magnetic anisotropy and the degree of the non-collinearity of Co4Nb2O9 accurately, which will be key information in understanding its unusual magnetoelectric coupling and strong polarisation.