Spin-Polarized Topological Phases in Graphene Nanoribbons with Non-Benzenoid Defects

We have used density functional theory calculations to demonstrate that the presence of unsaturated pentagon edge defects within an armchair graphene nanoribbon can generate highly ordered and robust spin states in this otherwise diamagnetic system. Such pentagon defects create disruption of the bipartite AB lattice of graphene in which the local defect state interferes quite weakly with the delocalized pi-electrons of the backbone that form topological phases. The incorporation of boron pairs among such nanoribbons changes the stability of the magnetic phases and provides supplemental magnetic robustness due to an additional local rupture potential introduced by the dopants. Although the presence of a metallic substrate influences the electronic and magnetic properties of most nanoribbons, the magnetic character of the modified nanoribbons is not completely screened by the metal. This work provides new molecular concepts in organic magnetism, where topological and robust magnetic phases may coexist.