Tuning electronic and magnetic properties of Fe-doped MgCl2 monolayer by charge doping: a first-principles study.

In this work, Fe doping is proposed for magnetism engineering of MgCl2 monolayer, where electronic and magnetic properties are further modified by hole and electron doping. At equilibrium, the MgCl2 monolayer is a two-dimensional (2D) insulator with a large band gap of 5.99 eV that is formed by the separation in energy of Mg-3s and Cl-3p orbitals. With Fe doping in this 2D material, significant magnetism is mainly produced by 3d electrons of the Fe impurity with an overall magnetic moment of 4.00 µ B, where neighboring atoms also make small contribution to the system magnetism. The Fe-3d orbital also generates mid-gap subbands that lead to the emergence of the half-metallicity. Increasing the Fe doping level, the magnetic semiconductor nature is obtained in 2Fe@MgCl2 (with two Fe atoms) and 3Fe@MgCl2 (with three Fe atoms) systems. However, the antiparallel spin alignment with zero total magnetic moment is stable in the former case, meanwhile the parallel spin coupling with large total magnetic moment of 12.00 µ B is stable in the latter case. Moreover, robust perpendicular magnetic anisotropy (PMA) is also confirmed with magnetic anisotropy energy up to 899.05 µeV. Hole doping induces the antiparallel-to-parallel spin alignment transition in the 2Fe@MgCl2 system regardless of hole amount, while the transition from parallel to antiparallel configuration for the 3Fe@MgCl2 system only takes place at a high level of holes. Meanwhile, electron doping remains the spin coupling in both systems. Hole doping also affects the magnetic anisotropy by inducing the PMA-to-IMA switching (IMA: in-plane magnetic anisotropy). In addition, electron doping can switch the electronic nature from magnetic semiconductor to half-metallic. Our findings demonstrate effective magnetism engineering of MgCl2 monolayer induced by Fe doping, where electronic and magnetic properties of the doped systems can be further controlled by charge doping towards selective spintronic applications.