High Contrast Thermal Conductivity Change in Ni–Mn–In Heusler Alloys near Room Temperature

Materials with an abrupt transition between a low and a high thermal conductance state at a critical temperature would be useful for thermal regulation applications. Here, the authors report a high contrast reversible thermal conductivity change through the thermally‐induced martensitic transition (MT) in Ni–Mn–In alloys. The authors measure the thermal conductivity of a wide temperature range 130 < T < 530 K using time‐domain thermoreflectance (TDTR). The thermal conductivity of these alloys increases from ≈7.0–8.5 W m −1 K −1 to ≈11.5–13.0 W m −1 K −1 through the MT near 300 K as temperature rises, with a rate of change among the highest yet reported in solid‐state materials with thermally‐induced phase transitions. Based on Hall resistivity measurements, the authors further show that the change of thermal conductivity is dominated by the electronic contribution, which results from a unique carrier mobility change through the MT. Their findings highlight the interplay between the structural disorders and the thermal transport in alloys through solid‐state phase transitions and open a new avenue in the search of high‐performance materials for thermal regulation.