▎ 摘　　要

Magnetic two-dimensional materials have potential application in next-generation electronic devices and have stimulated extensive interest in condensed matter physics and material fields. However, how to realize high-temperature ferromagnetism in two-dimensional materials remains a great challenge in physics. Herein, we propose an effective approach that the dimerization of magnetic ions in two-dimensional materials can enhance the exchange coupling and stabilize the ferromagnetism. Manganese carbonitride Mn2N6C6 with a planar monolayer structure is taken as an example to clarify the method, in which two Mn atoms are gathered together to form a ferromagnetic dimer of Mn atoms, and further these dimers are coupled together to form the overall ferromagnetism of the two-dimensional material. In the Mn2N6C6 monolayer, the near-room-temperature ferromagnetism with the Curie temperature of 272 K is determined by solving the Heisenberg model using the Monte Carlo simulation method. Thus, our work not only predicts a two-dimensional ferromagnetic material Mn2N6C6 but also opens a new avenue to realize the high-temperature two-dimensional ferromagnetism.