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. FeX3 (X = F, Cl, Br, and I) monolayers with intrinsic ferromagnetism are fabricated by density functional theory and confirmed by a global minimum search. FeX3 (X = F, Cl, Br, and I) show a FM ground state, while an AFM-ZZ order has the second lowest energy. FeX3 (X = F, Cl, Br, and I) have a Curie temperature (Tc) of 56, 716, 116, and 148 K, respectively. FeX3 (X = F and Cl) are bipolar magnetic semiconductors (BMSs), while FeX3 (X = Br and I) are half-semiconductors (HSCs). FeF3 has a direct gap of 4.78 eV, while FeX3 (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 FeX3 show good dynamical and thermal stability. Moreover, charge doping can transform FeCl3 from the BMS with an FM order to a half-metal (HM) with ferrimagnetic (Ferrim) or FM orders. However, FeI3 could be transformed from the HSC with an FM order into an HM with Ferrim or FM orders. The high Tc, large MAE, and tunable electromagnetic properties suggest that 2D FeX3 (X = F, Cl, Br, and I) are promising magnetic SCs for potential application in electronics and spintronics.