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.

We report NiCl ₃ monolayer as a novel near-room-temperature Chern insulator and Dirac spin-gapless semiconductor, rendering NiCl ₃ with great potential for spintronic application.

Antiferromagnetic (AF) spin devices could be one of the representative components for applications of spintronics thanks to the numerous advantages such as resistance to magnetic field perturbation, stray field-free operation, and ultrahigh device operation speed. However, detecting and manipulating the spin of AF materials is still a major challenge due to the absence of a net magnetic moment and spin degeneracy in the band structure. Bipolar antiferromagnetic semiconductors are promising solutions to these problems. Herein, using density functional theory calculations, we present asymmetrical functionalized double MXenes (Cr₂TiC₂FCl) that behave as a novel bipolar antiferromagnetic semiconductor (BAFS) with vanishing magnetism, in which the valence band and conduction band around the Fermi level exhibit opposite spin directions. Remarkably, gate voltage can manipulate the spin orientation of the AF Cr₂TiC₂FCl and lead to a transition from BAFS to half-metal antiferromagnets (HMAF). Moreover, the mixed functionalized double MXenes with various F/Cl concentrations show the BAFS feature due to the different chemical environment for the Cr atom. Our results presented herein open a new strategy towards AF spintronics and the realization of the AF spin field effect transistor.