TMB (TM = Cr, Fe) monolayers: a new type of room temperature antiferromagnetic topological nodal line semimetal.

Two-dimensional materials that combine magnetism and topology offer unique advantages in the fields of spintronics and quantum computing. However, the design of two-dimensional (2D) materials simultaneously integrating both properties remains a significant challenge. Through systematic first-principles calculations, we predict two highly stable two-dimensional transition metal borides (TMBs). Our results reveal that both structures are antiferromagnetic (AFM) Dirac nodal line semimetals (NLSMs) with multiple band crossings near the Fermi level. Under biaxial strain, FeB can be transformed into a ferromagnetic state under 2% tensile strain, which is further verified to possess Weyl nodal loops (Weyl NLs). This discovery provides novel insights for the regulation of magnetic topological materials and holds promising potential for applications in low-power-consumption spintronic devices.