Ultrahigh Lattice Thermal Conductivity in 2D Magnetic VSi₂N₄ Driven by Exceptional Stiffness

Two-dimensional (2D) magnetic semiconductors are promising candidates for next-generation spintronic, memory, and logic devices. However, their practical deployment is often hindered by poor heat dissipation due to the low lattice thermal conductivity (κ_L). Herein, we identify a 2D ferromagnetic semiconductor, VSi₂N₄, that exhibits an ultrahigh κ_L. Using first-principles calculations combined with the MACE machine learning potential and the phonon Boltzmann transport equation, we reveal that the room-temperature κ_L of VSi₂N₄ is about 317 Wm^-1K^-1. This value is one order of magnitude higher than that of most known 2D magnets and represents the highest κ_L reported in these materials. This superior thermal transport mainly originates from the large phonon group velocity and weak phonon-phonon scattering. Notably, even with the inclusion of four-phonon scattering, the κ_L reduction is merely approximately 8.3%, indicating limited high-order anharmonicity. Meanwhile, our analysis further reveals that the κ_L value of VSi₂N₄ significantly deviates from the conventional scaling trends established by Slack based on the number of atoms per unit cell and the average atomic mass. Nevertheless, a clear positive correlation is established with the Young’s modulus, underscoring mechanical stiffness as an effective descriptor for superior thermal transport in 2D systems. The exceptional stiffness of VSi₂N₄ is attributed to the strong bonding resulting from the highly localized charge distribution between the Si and N atoms. These findings presented in this work not only reveal VSi₂N₄ as a unique platform integrating robust ferromagnetism with outstanding heat dissipation, but also provide crucial guidance for the thermal management of future high-performance 2D magnetic materials.