Ferromagnetic Dirac half-metallicity in edge-modified zigzag boron nitride nanoribbons

Abstract

The discovery of one-dimensional (1D) materials and their applications in cutting-edge technologies like spintronics has led to extensive efforts being devoted to their theoretical and experimental research. Here, by using first principles density functional theory (DFT) calculations, we systematically investigate the properties of zigzag boron nitride nanoribbons (ZBNNRs) over edge passivation (X = H, F, Cl, NH₂, NO₂, OH, CH₃, and COOH), and varying widths. Numerical results demonstrate that single nitrogen edge passivation and both edge passivation show semiconducting and insulating behaviour, but single boron edge passivation shows fully spin-polarized Dirac fermions at the Fermi level in the minority spin, and the opposite spin has a tuneable band gap over a wide range (0.9–5.1 eV). Upon changing different chemical groups, the band gap between Dirac points can also be manipulated (0.01–0.14 eV). Ab initio molecular dynamics result in stable NRs at room temperature and Curie temperature for ZBNNRs-BX shows ferromagnetism (FM) above room temperature. Spin-polarized projected density of states (SP-PDOS) provides a detailed origin of edge states, their importance in metal to non-metal transition, as well as insights into the Dirac points. Interestingly SP-PDOS reveals that only bare edge states are responsible for electric flow and FM, independent of the NR width. Therefore, this work showcases intrinsic half metallicity and provides a detailed way of revealing the spin-polarized Dirac fermion nature of edge passivated ZBNNRs showing potential applications towards BN based, low consumption, and thermally stable spintronic nano-devices.