Predicted new 2D MoX3 (X = Ga, In, Tl) monolayer with giant magnetocrystalline anisotropy and near room-temperature antiferromagnetism

We predict new 2D MoX3 (X=Ga, In, Tl) monolayers using first-principles calculations. All MoX3 monolayers are structurally, dynamically, mechanically, and thermally stable, as evidenced by negative formation energies, satisfaction of the Born–Huang criteria, and the absence of imaginary phonon modes, with ab initio molecular dynamics further confirming stability at 300 K. The monolayers exhibit mixed covalent−ionic bonding between Mo and X atoms and display metallic behavior in all magnetic configurations. Magnetically, the MoX3 monolayers host diverse ground states arising from competing exchange interactions: MoGa3 stabilizes into an AFM3 state, MoIn3 adopts a ferromagnetic ground state, and MoTl3 favors AFM1 ordering. Exchange coupling parameters reveal strong sensitivity to X-site substitution, enabling tunable magnetic interactions. Remarkably large magnetocrystalline anisotropy energies (MAE) of 5.55 meV (MoGa3), 7.75 meV (MoIn3), and 40.90 meV (MoTl3) indicate robust perpendicular magnetic anisotropy in MoGa3 and MoIn3, while MoTl3 exhibits exceptionally strong in-plane anisotropy driven by enhanced Tl-induced spin–orbit coupling. Monte Carlo simulations predict ordering temperatures of 273.7, 172, and 223.2 K for MoGa3, MoIn3, and MoTl3, confirming near room-temperature antiferromagnetism in MoGa3 and MoTl3. The combination of high Néel temperatures, strong magnetic anisotropy, tunable exchange interactions, and intrinsic metallicity positions MoX3 monolayers as promising candidates for advanced spintronic applications. This study represents the first report of MoX3 monolayers incorporating group-13 elements (Ga, In, Tl), providing a versatile platform for designing functional 2D magnetic materials.