Unraveling the microscopic origin of out of plane magnetic anisotropy in VI3

Abstract

Intrinsic two-dimensional (2D) ferromagnetic (FM) semiconductors have attracted extensive attentions for their potential applications in next-generation spintronics devices. In recent years, the van der Waals material VI₃ has been experimentally found to be an intrinsic FM semiconductor. However, the electronic structure of the VI₃ is not fully understood. To reveal why the VI₃ is a ferromagnetic semiconductor with strong out-of-plane anisotropy, we systematically studied the electronic structure of the monolayer VI₃. Our results confirm that the monolayer VI₃ is a Mott insulator, and d² electrons occupy a_g and $e_g^{\pi +}$ orbitals. The half-metallic state is a metastable state with a total energy 0.7 eV higher than the ferromagnetic Mott insulating state. Furthermore, our study confirmed that the VI₃ exhibits the out-of-plane magnetic anisotropy, which originates from d² electrons occupying low-lying a_g and $e_g^{\pi +}$ orbitals. Since the orbital angular momentum of the $e_g^{\pi +}$ state is not completely quenched, the VI₃ has the out-of-plane anisotropy under interplay between the spin-orbit coupling and crystal field. Our study provides valuable guidance for the design of 2D magnetic materials with pronounced out-of-plane anisotropy.