Pnictogen-codoping-induced magnetic anisotropy switching in Mn-doped WSTe Janus monolayers: a first-principles study

In this work, magnetism engineering of the WSTe Janus monolayer is investigated using first-principles calculations. The pristine monolayer is a nonmagnetic semiconductor with an indirect band gap of 1.24 eV. Monolayer magnetization with a magnetic semiconductor nature is achieved by doping with P atoms, whereas As doping preserves the nonmagnetic nature and causes metallization of the monolayer. It is found that Mn doping leads to the emergence of ferromagnetism with a high Curie temperature of up to 876.13 K. In-plane magnetic anisotropy (IMA) is induced at small Mn-Mn separations (2Mn₁), whereas larger separations (2Mn₂) lead to the emergence of perpendicular magnetic anisotropy (PMA). Codoping with pnictogen atoms weakens the ferromagnetism in the Mn-doped systems, resulting in reduced Curie temperatures. Interestingly, the presence of additional pnictogen atoms leads to IMA-to-PMA switching in the 2Mn₁-doped system, and PMA-to-IMA switching in the case of the 2Mn₂ doping configuration. In all cases, a magnetic semiconductor nature is obtained, which could be enhanced by pnictogen codoping. Our results introduce Mn doping as an effective method to induce magnetic states in the WSTe Janus monolayer, where the magnetic anisotropy could be controlled by codoping with P and As atoms. These findings provide valuable theoretical guidance for tailoring the WSTe Janus monolayer for applications in magnetic-field sensing and magnetic-random-access-memory (MRAM) devices.