Modulation of electronic and magnetic properties of defective and TM-doped Al₂SSe Janus monolayer (TM = Mn and Fe)...

Effective manipulation of electronic and magnetic properties plays a key role in designing practical applications of materials. In this work, the magnetism engineering in Al₂SSe monolayers is studied by creating pair Al (pVa) vacancies and doping with a pair of TM transition metals (pTM = Mn and Fe). Further, electronic and magnetic properties are modulated through hole and electron doping. The pristine Al₂SSe monolayer is intrinsically nonmagnetic, exhibiting an indirect gap of 2.04 eV. The creation of pVa-type defects induces half-metallicity, in-plane magnetic anisotropy (IMA), and an overall magnetic moment of 2.00 µ _B. In this case, first neighbor Se atoms and second neighbor Al atoms from defect sites primarily originate the system magnetic moment. The magnetism of the pVa@mo system can be significantly enhanced by electron doping that increases the magnetic moment and strengthens the IMA. Significant monolayer magnetization is also achieved by pTM doping, where impurities produce mainly magnetic properties. Paired Mn atoms show antiparallel spin alignment to form the ferrimagnetic (FiM) state of the pMn@mo system, which becomes weaker with electron doping. Meanwhile, the ferromagnetic (FM) state is stable in the pFe@mo system with parallel spin orientation of Fe impurities, which becomes much stronger with electron doping. Herein, a high Curie temperature of 972.40 K is obtained for the pFe@mo system, which increases considerably by electron doping. In addition, the electronic properties and magnetic anisotropy can be effectively controlled by varying carrier concentration. Our findings solidly pave the way to make artificially two-dimensional magnetic materials from the Janus monolayer Al₂SSe, where further hole and electron doping can modulate the electronic and magnetic properties of the defective and doped systems towards selective spintronic applications.