Prediction of room-temperature ferromagnetism and large perpendicular magnetic anisotropy in a planar hypercoordinate FeB monolayer.

Two-dimensional (2D) magnets simultaneously possessing a high transition temperature and large perpendicular magnetic anisotropy are extremely rare, but essential for highly efficient spintronic applications. By using ab initio and global minimization approaches, we for the first time report a completely planar hypercoordinate metalloborophene (α-FeB3) with high stability, unusual stoichiometry and exceptional magnetoelectronic properties. The α-FeB3 monolayer exhibits room-temperature ferromagnetism (Tc = 480 K), whose origin is first revealed by the B-mediated RKKY interaction in the 2D regime. Its perpendicular magnetic anisotropy is almost six times larger than that of the experimentally realized 2D CrI3 and Fe3GeTe2. Moreover, metallic α-FeB3 shows n- and p-type Dirac transport with a high Fermi velocity in both spin channels. Our results not only highlight a promising 2D ferromagnet for advanced spintronics, but also pave the way for exploring novel 2D magnetism in boron-based magnetic allotropes.