An ab initio study of transition metals doped with WSe2 for long-range room temperature ferromagnetism in two-dimensional transition metal dichalcogenide.

We report a systematic study of the magnetic properties in transition metals doped with WSe2 through the use of first principle calculations. The results demonstrate the possibility of generating long-range room temperature ferromagnetic interaction in WSe2 with the use of Mn and Fe doping. In the case of Fe, a percolation threshold is required for long-range ferromagnetism, whereas the long-range room temperature ferromagnetic interaction in Mn-doped WSe2 persists even at a low concentration (~5.6%). The ferromagnetism is mediated by the delocalized p states in the Se atoms, which couple antiferromagnetically with the spin-down a1 and e1 states in Fe doping through a correlated interaction. In Mn doping, the p states of Se tend to couple ferromagnetically with the 3d state of Mn, which stabilizes the long-range ferromagnetism between the Mn ions, although the short-range interaction is antiferromagnetic. In addition, the calculations indicate that Fe and Mn tend to configure at a high spin state, thus they possess much larger magnetic moments in WSe2 than when they are doped into other transition metal dichalcogenides. We also discovered a strong dependence of the exchange interaction on the dopants' spatial positions, distances, and concentrations, which alters the magnetic coupling from strong ferromagnetism to strong antiferromagnetism. These results can provide useful guidance to engineer the magnetic properties of WSe2 in future experiments.