Li₂NiSe₂: A new-type intrinsic two-dimensional ferromagnetic semiconductor above 200 K

By using first-principles electronic structure calculations, we propose a two-dimensional ferromagnetic semiconductor Li 2 NiSe 2 with a Curie temperature above 200 K. The structure of monolayer Li 2 NiSe 2 is dynamically stable, which is derived from the synthesized prototype compound Li 2 NiO 2 and can be denoted as Li-decorated 1T-type NiSe 2 . The Ni–Se–Ni ferromagnetic superexchange dominates the magnetic couplings between the Ni atoms, which can be understood in the frame of the Goodenough–Kanamori–Anderson (GKA) rules. Our systematic study of monolayer Li 2 NiSe 2 enables its promising applications in spintronics and suggests a new choice to design two-dimensional ferromagnetic semiconductors.