Large Magnetothermal Conductivity Of Homno3 Single Crystals And Its Relation To The Magnetic-Field-Induced Transitions Of Magnetic Structure

We study the low-temperature heat transport of HoMnO3 single crystals to probe the magnetic structures and their transitions induced by magnetic field. It is found that the low-T thermal conductivity (kappa) shows very strong magnetic-field dependence, with the strongest suppression of nearly 90% and the biggest increase of 20 times of kappa compared to its zero-field value. In particular, some "dip"-like features show up in kappa(H) isotherms for field along both the ab plane and the c axis. These behaviors are found to shed light on the complex H-T phase diagram and the field-induced reorientations of Mn3+ and Ho3+ spin structures. The results also demonstrate a significant spin-phonon coupling in this multiferroic compound.