Half-metallicity in graphene nanoribbons with topological line defects

First-principles calculations have been performed to investigate the electronic properties of graphene nanoribbons with topological line defects composed of octagons and fused pentagons. We find that the edge-passivated zigzag graphene nanoribbons (ZGNRs) with the line defects along the edge show half-metallicity as the line defect is close to one edge. The electronic properties of the ZGNRs with line defects can be tuned by changing the ribbon width and the position of the line defect. When the position of the line defect changes, there are transitions from an antiferromagnetic semiconductor to an antiferromagnetic half-metal, and then to a ferromagnetic metal, suggesting the potential applications of the system in spintronic devices.