Multiferroics, in which dielectric and magnetic orders coexist and couple with each other, attract renewed interest for their cross-correlated phenomena offering a fundamental platform for novel functionalities. Elementary excitations in such systems are strongly affected by the lattice–spin interaction, as exemplified by the electromagnons and the magneto-thermal transport. Here we report an unprecedented coupling between magnetism and phonons in multiferroics, namely, the giant thermal Hall effect. The thermal transport of insulating polar magnets (ZnxFe1−x)2Mo3O8 is dominated by phonons, yet extremely sensitive to the magnetic structure. In particular, large thermal Hall conductivities are observed in the ferrimagnetic phase, indicating unconventional lattice–spin interactions and a new mechanism for the Hall effect in insulators. Our results show that the thermal Hall effect in multiferroic materials can be an effective probe for strong lattice–spin interactions and provide a new tool for magnetic control of thermal currents.

Nature Materials (2017) doi:10.1038/nmat4905
Received 15 October 2016 Accepted 07 April 2017 Published online 15 May 2017

http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat4905.html