Tailing the Magnetoelectric Properties of 2H-MoS2 by Engineering Covalently Bonded Mo Self-intercalation: Ferromagnetic Materials

Two-dimensional (2D) intrinsic ferromagnetic (FM) materials play a crucial role in spintronics. Through a systematic research of the 2H-MoS₂ bilayer (BL) with self-intercalation (SI) of Mo atom, we have discovered that SI can introduce a long-range magnetic order, as Mo_SI atoms lose electrons. The MoS₂ BLs (Mo_mS_n) with self-intercalated Mo (Mo_SI) atoms show antiferromagnetic (AFM) order under a high concentration of Mo_SI atoms, where the direct exchange interaction dominates over the superexchange interaction. Mo_mS_n becomes half-metal (HM) with interlayer FM order after Mo’s self-intercalation, under lower Mo_SI atom concentrations, independent of the stacking orders. Mo₉S₁₆-AA exhibits HM with FM order, with a corresponding Curie temperature (T_c) of 35 K. Mo_mS_n-AA and AB stackings with a lower concentration of Mo_SI atoms transform into half semiconductors (HSCs). Moreover, the magnetic anisotropy energies (MAEs) of Mo₉S₁₆-AA and AB stackings are −0.080 and −1.06 meV/f.u., suggesting that the magnetic easy axis (EA) of Mo_mS_n tends to the [100] direction, regardless of the stacking orders. However, the MAEs of Mo_mS_n-AA and AB stackings differ due to variations in the hybridization interaction between Mo’s d orbitals. The formation energies of Mo_mS_n change with the chemical potential of S (μ_s) and the concentration of Mo_SI atoms. Furthermore, the formation energy (ε_f) monotonically increases as the concentration of Mo_SI monotonically increases. Additionally, Mo_mS_n with Mo_SI atoms could be synthesized under a higher chemical potential of Mo atom (μ_Mo). The Mo_mS_n-AB stackings are always more stable than the AA stackings. Self-intercalated Mo_mS_n exhibits good dynamic and thermal stability at 300 and 600 K, respectively. These findings suggest a promising approach to introducing a modulated long-range FM order and electromagnetic properties into 2H-MoS₂ and other transition metal dichalcogenides (TMDs).