Anionic electron dimensionality and monolayer ferromagnetism in Y–Co electrides

Electrides, characterized by spatially confined anionic electrons, have emerged as a promising class of materials for catalysis, magnetism, and superconductivity. However, transition-metal-based electrides with diverse electron dimensionalities remain largely unexplored. Here, we perform a comprehensive first-principles investigation of Y–Co electrides, focusing on Y₃Co, Y₃Co₂, and YCo. Our calculations reveal a striking dimensional evolution of anionic electrons: from two-dimensional (2D) confinement in YCo to one-dimensional (1D) in Y₃Co₂ and zero-dimensional (0D) in Y₃Co. Remarkably, the YCo monolayer exhibits intrinsic ferromagnetism, with a magnetic moment of 0.65 μ_B per formula unit arising from spin-polarized anionic electrons mediating long-range coupling between Y and Co ions. The monolayer also shows a low exfoliation energy (1.66 J/m²), indicating experimental feasibility. All three electrides exhibit low work functions (2.76 eV–3.11 eV) along with Co-centered anionic states. This work expands the family of transition-metal-based electrides and highlights dimensionality engineering as a powerful strategy for tuning electronic and magnetic properties.