Dimension reduction induced anisotropic magnetic thermal conductivity in hematite nanowires

The thermophysical properties near the magnetic phase transition point is of great importance in the study of critical phenomenon. Low-dimensional materials are suggested to hold different thermophysical properties comparing to their bulk counterpart due to the dimension induced quantum confinement and anisotropy. In this work, we measured the thermal conductivity of alpha-Fe2O3 nanowires along the [110] direction (growing direction) with temperature from 100 to 150 K and found a dip of thermal conductivity near the Morin temperature. We found that the thermal conductivity near Morin temperature varies with the angle between magnetic field and the [110] direction of nanowire. More specifically, an angular-dependent thermal conductivity is observed, due to the magnetic field induced movement of the magnetic domain wall. The angle corresponding to the maximum of thermal conductivity varies near the Morin transition temperature, due to the different magnetic easy axis as suggested by our calculation based on magnetic anisotropy energy. This angular dependence of thermal conductivity indicates that the easy axis of alpha-Fe2O3 nanowires is different from bulk alpha-Fe2O3 due to the geometric anisotropy.