A systematic investigation on chalcogen vacancies, doping with transition metals, and their complexes in Janus monolayer WSeTe

In this work, the impacts of chalcogen vacancies and doping with transition metals (Mn and Fe), as well as their complexes, on the electronic and magnetic properties of Janus monolayer WSeTe are investigated using first-principles calculations. Pristine monolayer has good structural stability and exhibits the direct-gap semiconductor nature with a band gap of 1.34 eV. The band gap reductions of the order of 19.40% and 23.88% are obtained by creating single Se and Te vacancies, respectively. Mn doping induces magnetic semiconductor nature with the in-plane magnetic anisotropy (IMA), while the half-metallicity with perpendicular magnetic anisotropy (PMA) is obtained by Fe doping. Further, the effects of vacancy+impurity complexes are examined. Calculations suggest the enhanced magnetic anisotropy of Mn- and Fe-doped WSeTe monolayer by means of creating additional single vacancies. In all cases, magnetic properties are produced primarily by $3d$ orbital of Mn and Fe atoms, where smaller contributions from the host W, Se, and Te atoms are also observed. Importantly, the antiparallel spin coupling between Mn/Fe and W-Se-Te atoms is confirmed. In addition, the calculated cohesive energies and ab initio molecular dynamics (AIMD) simulations confirm good structural stability of all the defected/doped WSeTe systems, suggesting their experimental feasibility. Our findings may introduce efficient methods to induce magnetism in Janus monolayer WSeTe with feature-rich electronic natures towards spintronic applications.