Vacancies Engineering in Molybdenum Boride MBene Nanosheets to Activate Room-Temperature Ferromagnetism

The rapid development of low energy dissipation spintronic devices has stimulated the search for air-stable 2D nanomaterials possessing room-temperature ferromagnetism. Here the experimental realization of 2D Mo_4/3B₂ nanosheets is reported with intrinsic room-temperature ferromagnetic characteristics by vacancy engineering. These nanosheets are synthesized by etching the bulk MAB phase (Mo_2/3Y_1/3)₂AlB₂ into Mo_4/3B₂ nanosheets in ZnCl₂ molten salt. The Mo_4/3B₂ nanosheets show robust intrinsic ferromagnetic properties, with a saturation magnetic moment of 0.044 emu g^-1 at 300 K, while vacancy-free MoB MBene exhibits paramagnetism. It is elucidated that the Mo-vacancy defect generates large density of states near the Fermi surface and spontaneously spin-split bands through first-principles calculations, which contributes to the non-zero magnetic moment in Mo_4/3B₂ nanosheets. This work lays the groundwork for activating the magnetic properties of MBene nanosheets by vacancy engineering, offering the possibilities for development of practical spintronic devices.