Two-dimensional (2D) transition metal nitrides have a wide prospect of applications in the fields of physics, chemistry, materials, etc. However, 2D transition metal nitrides with strong magnetism, especially high Neˊel temperature, are very scarce. Based on the first-principles calculations within the framework of density functional theory, we design two 2D transition-metal nitrides \textit{M}2N2 (\textit{M} = Ti, Co), in which the transition metal atoms and the N atoms form a 2D layer with a wrinkled structure. The structural stability is demonstrated by the cohesive energy, formation energy, elastic constants, phonon spectra and molecular dynamics simulations. Elastic moduli calculations reveal that the mechanical properties of the two structures are anisotropic. Spin-polarized calculations show that Ti2N2 is a 2D ferromagnetic material while Co2N2 is a 2D antiferromagnetic semimetal with a Dirac point at Fermi level. Furthermore, by solveing the Heisenberg model by Monte Carlo method, we discover that the 2D Co2N2 layer is a high-temperature antiferromagnetic material and the Neˊel temperature is up to 474 K. Therefore, our findings provide a rare antiferromagnetic 2D material with both high critical temperature and Dirac Fermions.
@article{arxiv.2503.12413,
title = {Antiferromagnetic two-dimensional transition-metal nitride Co$_2$N$_2$ layer with high N$\rm \acute{\textbf e}$el temperature and Dirac fermions},
author = {Lujia Tian and Lihui Han and Yuanfang Yue and Huazhen Li and Z. Y. Xie and Xun-Wang Yan},
journal= {arXiv preprint arXiv:2503.12413},
year = {2025}
}