Prediction of the TiS₂ Bilayer with Self-Intercalation: Robust Ferromagnetic Semiconductor with a High Curie Temperature

Abstract

The search for new two-dimensional magnetic materials has been a hot topic since the discovery of graphene in 2004 as these materials play a crucial role in fields such as spintronics. In this study, we systematically investigated the 2H-TiS 2 bilayer with self-intercalation (SI) of the Ti atom, revealing that SI can introduce magnetism to a nonmagnetic 2H-TiS 2 . Taking Ti 19 S 36 -AB stacking as an example, we find that 2H–SI–TiS 2 exhibits a ferromagnetic order with a Curie temperature of 377 K. Ti 19 S 36 shows perpendicular magnetic anisotropy, with a magnetic anisotropy energy (MAE) of 7.43 × 10 –2 meV. Additionally, the MAE increases as the self-intercalated Ti’s (Ti SI ) concentration ( x ) decreases, attributed to the enhanced hybridization interaction between the d x 2 – y 2 and d xy orbitals of Ti atoms. Ti 19 S 36 -AB stacking is identified as a bipolar magnetic semiconductor (BMS) with an indirect band gap of 0.53 eV. As x increases, Ti m S n transitions from BMS to half-semiconductor (HSC) and metal and then back to HSC, demonstrating a rich phase. Ti m S n shows good dynamic and thermodynamic stabilities at 300 and 500 K, respectively. Furthermore, the formation energy (ε f ) of Ti m S n increases monotonically with rising x . Moreover, Ti m S n can be easily synthesized under higher μ Ti . The migration barrier of Ti SI between adjacent coordination sites is 0.740 eV, further confirming the stability of the self-intercalated structure. These findings imply the potential of 2H-TiS 2 and nonmagnetic transition metal dichalcogenides in spintronics.