Stoner Ferromagnetism in Intrinsic BeC₅ Monolayer

The diamagnetism of graphene restricts its suitability as a candidate material for future spintronic applications. In this study, we unveil the inherent ferromagnetism by deliberately incorporating zigzag beryllium chains into the structure of graphene. Using swarm-intelligence structure search methods and first-principles calculations, we have predicted a global minimum BeC 5 monolayer, demonstrating an intrinsic magnetic moment of 0.65 μ B per unit cell. Notably, the BeC 5 monolayer exhibits a node-line-like characteristic at the Fermi level, giving rise to a high density of states and a pronounced Van Hove singularity. The distinct electronic structure activates Stoner’s criterion, resulting in the onset of ferromagnetic instability in BeC 5 . Monte Carlo simulations utilizing the Ising model indicate a Curie temperature of 80 K for BeC 5 . Our study illustrates the sensitivity of ferromagnetic instability to biaxial tensile strain, with the transition from ferromagnetism to nonmagnetism taking place at a critical strain of 4.6%. This transition is accompanied by the emergence of Dirac states within the system.