Prediction of High Curie Temperature, Large Magnetic Crystal Anisotropy, and Carrier Doping-Induced Half-Metallicity in Two-Dimensional Ferromagnetic FeX₃ (X = F, Cl, Br, and I) Monolayers

Two-dimensional (2D) intrinsic ferromagnetic (FM) semiconductors (SCs) are urgent for spintronics. FeX 3 (X = F, Cl, Br, and I) monolayers with intrinsic ferromagnetism are fabricated by density functional theory and confirmed by a global minimum search. FeX 3 (X = F, Cl, Br, and I) show a FM ground state, while an AFM-ZZ order has the second lowest energy. FeX 3 (X = F, Cl, Br, and I) have a Curie temperature ( T c ) of 56, 716, 116, and 148 K, respectively. FeX 3 (X = F and Cl) are bipolar magnetic semiconductors (BMSs), while FeX 3 (X = Br and I) are half-semiconductors (HSCs). FeF 3 has a direct gap of 4.78 eV, while FeX 3 (X = Cl, Br, and I) have indirect band gaps of 2.92, 2.36, and 1.69 eV, respectively. They show perpendicular magnetic anisotropy, with a magnetic anisotropy energy (MAE) of 0.08, 0.11, 0.59, and 3.19 meV, respectively. All FeX 3 show good dynamical and thermal stability. Moreover, charge doping can transform FeCl 3 from the BMS with an FM order to a half-metal (HM) with ferrimagnetic (Ferrim) or FM orders. However, FeI 3 could be transformed from the HSC with an FM order into an HM with Ferrim or FM orders. The high T c, large MAE, and tunable electromagnetic properties suggest that 2D FeX 3 (X = F, Cl, Br, and I) are promising magnetic SCs for potential application in electronics and spintronics.