Long-range ferromagnetic ordering in manganese-doped two-dimensional dichalcogenides

We report an investigation of long-range ferromagnetic (FM) ordering in Mn-doped MoS₂, MoSe₂, MoTe₂, and WS₂ for Mn concentration less than 5$%$ using density functional theory calculations. The long-range ferromagnetism of Mn spins is mediated by an antiferromagnetic (AFM) exchange between the localized Mn d states and the delocalized p states of the S, Se, and Te atoms. In contrast, transition metals like Fe, Co, and Ni show a FM exchange with the S, Se, and Te atoms, which results in a very weak FM (even slightly AFM) coupling for transition-metal defects with large separations. The Mn substitution at Mo or W sites is energetically favorable, thus making the Mn-doped dichalcogenides promising candidates for two-dimensional dilute magnetic semiconductors.