Low-Temperature Heat Transport, Specific Heat, And Magnetic Properties Of The Hexagonal Tmmno3 Single Crystals

We study the low-temperature heat transport, as well as the magnetization and the specific heat, of TmMnO3 single crystals to probe the transitions of magnetic structure induced by magnetic field. It is found that the low-T thermal conductivity (kappa) shows strong magnetic-field dependence and the overall behaviors can be understood in the scenario of magnetic scattering on phonons. In addition, a strong "diplike" feature shows up in kappa(H) isotherms at 3.5-4 T for H vertical bar vertical bar c, which is related to a known spin reorientation of Mn3+ moments. The absence of this phenomenon for H vertical bar vertical bar a indicates that the magnetic-structure transition of TmMnO3 cannot be driven by the in-plane field. In comparison, the magnetothermal conductivity of TmMnO3 is much larger than that of YMnO3 but smaller than that of HoMnO3, indicating that the magnetisms of rare-earth ions are playing the key role in the spin-phonon coupling of the hexagonal manganites.