Intrinsic Ferromagnetism in Mn-Substituted MoS₂ Nanosheets Achieved by Supercritical Hydrothermal Reaction

Doping atomically thick nanosheets is a great challenge due to the self-purification effect that drives the precipitation of dopants. Here, a breakthrough is made to dope Mn atoms substitutionally into MoS₂ nanosheets in a sulfur-rich supercritical hydrothermal reaction environment, where the formation energy of Mn substituting for Mo sites in MoS₂ is significantly reduced to overcome the self-purification effect. The substitutional Mn doping is convincingly evidenced by high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine spectroscopy characterizations. The Mn-doped MoS₂ nanosheets show robust intrinsic ferromagnetic response with a saturation magnetic moment of 0.05 µ_B Mn^-1 at room temperature. The intrinsic ferromagnetism is further confirmed by the reversibility of the magnetic behavior during the cycle of incorporating/removing Li codopants, showing the critical role of Mn 3d electronic states in mediating the magnetic interactions in MoS₂ nanosheets.