LAUSR

Based on first-principles calculations, we discover a two-dimensional layered antiferromagnetic (AFM) electride Gd2O, where anionic excess electrons exist in the interstitial spaces between positively charged cationic layers. It is revealed that each cationic layer composed of three-atom-thick Gd−O−Gd stacks has inplane ferromagnetic and out-of-plane AFM superexchange interactions between the localized Gd 4f spins through O 2p orbitals. Furthermore, the interlayer superexchange mediated by the hybridized Gd-5d and interstitial-s-like states involves intimate couplings between the spin, lattice, and charge degrees of freedom, thereby inducing simultaneous magnetic, structural, and electronic phase transitions. The resulting ground state with the simple hexagonal lattice hosts massless Dirac fermions protected by nonsymmorphic magnetic symmetry, as well as massive Dirac fermions. We thus demonstrate that the anionic excess electrons in Gd2O play a crucial role in the emergence of magnetic Dirac semimetal states, therefore offering an intriguing interplay between 2D magnetic electrides and topological physics.