Dimension reduction induced anisotropic magnetic thermal conductivity in hematite nanowire

TL;DR

This study investigates how magnetic phase transitions and anisotropy influence thermal conductivity in hematite nanowires, revealing angular-dependent effects linked to magnetic domain wall movement and easy axis shifts.

Contribution

It demonstrates the impact of magnetic anisotropy and geometric confinement on thermal conductivity near the Morin transition in hematite nanowires, highlighting differences from bulk material.

Findings

Thermal conductivity dips near Morin temperature.

Thermal conductivity varies with magnetic field angle.

Easy axis of nanowires differs from bulk hematite.

Abstract

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 $\alpha$-Fe$_2$O$_3$ nanowires along [110] direction (growing direction) with temperature from 100K to 150K and found a dip of thermal conductivity near the Morin temperature. We found the thermal conductivity near Morin temperature varies with the angle between magnetic field and [110] direction of nanowire. More specifically, an angular-dependent thermal conductivity is observed, due to the magnetic field induced movement of 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 $\alpha$-Fe$_2$O$_3$ nanowires is different from bulk $\alpha$-Fe$_2$O$_3$ due to the geometric anisotropy.