The Dirac half-metallicity (H. Ishizuka et al., Phys. Rev. Lett. 2012, 109, 237207, Li et al. Phys. Rev. B: Condens. Matter Mater. Phys., 2015, 92, 201403(R)) with a gap in one spin channel but a Dirac cone in the other has been proposed and attracted considerable attention. We report these exciting properties for VCl₃ and VI₃ layered materials based on density functional theory combined with the self-consistently determined Hubbard U approach (DFT+U_scf). Using DFT+U_scf, the stability and electronic and magnetic structures of VCl₃ and VI₃ monolayers are systematically investigated. The DFT+U_scf shows that VCl₃ and VI₃ monolayers have intrinsic ferromagnetism and half-metallicity. Remarkably, the VCl₃ and VI₃ monolayers possess a rather rare half-metallic Dirac point around the Fermi level with just one spin channel. In contrast to the Dirac point in graphene, the Dirac points in VCl₃ and VI₃ monolayers are mainly due to the V-d electrons and consequently they show a large spin–orbital coupling induced gaps of about 29 meV and 12 meV for VCl₃ and VI₃ monolayers, respectively. The Monte Carlo simulations based on the Ising model demonstrate that the Curie temperatures of VCl₃ and VI₃ sheets are only 80 K and 98 K, respectively. However, the Curie temperature can be increased up to room temperature by carrier doping. The feasibility of an exfoliation from VCl₃ and VI₃ layered bulk phases is confirmed due to the small cleavage energies. Our results greatly broaden the family of potential 2D Dirac materials. The calculated properties of VCl₃ and VI₃ monolayers show that these materials have great application potential, opening the way towards the development of high-performance electronic devices.

Magnetic properties of Mn₂CT₂ (T = F, Cl, OH, O, and H) MXenes are reported based on a computational investigation.

Searching for two-dimensional (2D) materials with room-temperature magnetic order and high spin-polarization is essential for the development of next-generation nanospintronic devices. A new class of 2D magnetic materials with high Néel temperature, fully compensated antiferromagnetic order (zero magnetization) and completely spin-polarized semiconductivity is proposed for the first time. Based on the density functional theory calculations, we predict these properties for asymmetrically functionalized MXenes (Janus Cr₂C) – Cr₂CXX′ (X, X′ = H, F, Cl, Br, OH). The valence and conduction bands in these materials are made up of opposite spin channels and they can behave as bipolar magnetic semiconductors with zero magnetization. A Néel temperature as high as 400 K has been found for Cr₂CFCl, Cr₂CClBr, Cr₂CHCl, Cr₂CHF, and Cr₂CFOH materials. Remarkably, the spin carrier orientation and induced transition from bipolar magnetic semiconductors to half-metal antiferromagnets can be easily controlled by electron or hole doping. The band gap of Janus MXenes can be effectively tuned by the selection of a pair of chemical elements/functional groups terminating the upper and the lower surfaces. The spin-polarized semiconductivity with zero magnetism is preserved when MXenes are put on the SiC(0001) support. The results presented herein open a new road towards the construction of 2D high-temperature spin-polarized materials with antiferromagnetism potentially suitable for spintronic applications.