The Defect Charge Effect on Magnetic Anisotropy Energy and Dzyaloshinskii–Moriya Interaction of the I Vacancy and 3d Transition Metal Co-Doped Monolayer CrI3

Recently, significant effort has been devoted to enhancing magnetic anisotropy energy (MAE) and the Dzyaloshinskii–Moriya interaction (DMI) in two-dimensional (2D) ferromagnetic materials through various tuning approaches. Among these methods, defect engineering is one of the most effective strategies. However, the influence of these charged defects on the MAE and DMI is unclear. Therefore, we systematically investigate the defect effect on the MAE and DMI of I vacancy-doped (vI-CrI3), 3d-transition-metal-doped (TM = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) (3d-TMi@CrI3), and vI-TM co-doped (3d-TMi@vI-CrI3) monolayer CrI3 using first-principles calculations. Our results indicate that Cr-rich conditions can promote the defect formation of vI-CrI3, 3d-TMi@CrI3, and 3d-TMi@vI-CrI3 systems and demonstrate that 49 types of charged systems are stable. Among these systems, the Cui@vI-CrI3 in the +1 charge state (Cui•@vI-CrI3) system has a smaller defect formation energy, exhibiting a large MAE exceeding 30 meV, and the ratio (D/J) of the antisymmetric magnetic exchange parameter (D) to the Heisenberg exchange parameter (J) reaches 1.04. The large MAE originates from the transition from single-ion anisotropy (SIA) to covalent interaction anisotropy (CIA) due to the coupling variation between the py and px orbitals of I atoms near the Fermi level caused by charge states. The enhancement of the DMI is due to the electrostatic potential differences between the I-top and I-bottom layers, which are conducive to forming stable chiral spin textures. This study provides insight into the defect charge state modulating the magnetism of 2D magnetic materials.