Cu3Nb2O8: a multiferroic with chiral coupling to the crystal structure

Now published in Physical Review Letters!

By combining bulk properties, neutron diffraction and non-resonant X-ray diffraction measurements, we demonstrate that the new multiferroic Cu3Nb2O8 becomes polar simultaneously with the appearance of generalised helicoidal magnetic ordering. The electrical polarization is oriented perpendicularly to the common plane of rotation of the spins — an observation that cannot be reconciled with the “conventional” theory developed for cycloidal multiferroics. Our results are consistent with coupling between a macroscopic structural rotation, which is allowed in the paramagnetic group, and magnetically-induced structural chirality.


R. D. Johnson, Sunil Nair, L. C. Chapon, A. Bombardi, C. Vecchini, D. Prabhakaran, A. T. Boothroyd, and P. G. Radaelli, Phys. Rev. Lett. 107, 137205 (2011)