Lattice thermal conductivity switching via structural phase transition in ferromagnetic VI₃

Abstract

The realization of reversible thermal conductivity through ferromagnetic ordering can improve the heat management and energy efficiency in magnetic materials-based devices. VI3, as a new layered ferromagnetic semiconductor, exhibits a structural phase transition from monoclinic (C2/m) to rhombohedral (R3) phase as temperature decreases, making it a suitable platform to investigate thermal switching in magnetic phase transition materials. This work reveals that the thermal switching ratio of VI3 can reach 3.9 along the a-axis. Mechanical properties analysis indicates that the C2/m structure is stiffer than R3 one, causing the larger phonon velocity in C2/m phase. Moreover, due to the fewer phonon branches in C2/m phase, the number of phonon-phonon scattering channels in C2/m phase is smaller compared to R3 phase. Both the larger phonon velocity and the longer phonon lifetime lead to larger lattice thermal conductivity in C2/m phase. This study uncovers the mechanical and thermal properties of VI3, which provides useful guides for designing magnetic materials-based devices such as thermal switch.