Antiferromagnetic semiconductor nature in a GeS₂ monolayer doped with Mn and Fe transition metals

The absence of intrinsic magnetism in two-dimensional (2D) materials demands functionalization as necessary for broadening their applications. In this work, doping with transition metals (Mn and Fe) is proposed to modify the electronic and magnetic properties of a GeS₂ monolayer. A pristine monolayer is an indirect gap semiconductor with an energy gap of 0.73(1.47) eV computed by using the PBE(HSE06) functional. Significant magnetism with a total magnetic moment of 1.18<i>μ</i>_B emerges in the GeS₂ monolayer upon creating a single Ge vacancy, which is produced mainly by six nearest neighboring S atoms. In this case, the monolayer is metallized with S-p_{<i>x</i>,<i>y</i>} states responsible. Similarly, the magnetization of the GeS₂ monolayer is also achieved by doping with Mn and Fe atoms with total magnetic moments of 3.00 and 3.78<i>μ</i>_B, respectively. The calculated band structures imply that the magnetic semiconductor nature with a spin-up/spin-down gap of 0.72/0.53 eV is induced by Mn impurity, while doping with Fe atoms leads to monolayer metallization. Being surrounded by more electronegative S atoms, Mn and Fe impurities lose charge amounts of 1.19 and 1.11<i>e</i>, respectively. Further investigations on spin coupling indicate the antiferromagnetic semiconductor nature in Mn- and Fe-doped systems, regardless of the distance between impurities. Our results provide important insights into the effects of doping into the GeS₂ monolayer, which demonstrate that the doped systems hold promise for spintronic applications.