  It is well-known that ferromagnetism can be realized along the zigzag
graphene nanoribbon edges, but the armchair graphene nanoribbon edges (AGNEs)
are nonmagnetic. Here, we achieve Heisenberg antiferromagnetic spin chains
through edge reconstruction along the AGNEs. The reconstructed edge consists of
pentagonal carbon rings or a hybrid of pentagonal and hexagonal carbon rings.
The resultant nanoribbons are narrow-gap semiconductors and the band edge
states are either spin-degenerate edge states or nonmagnetic bulk states. The
spin is located on the outermost carbon of the pentagonal ring, and the
inter-spin exchange is the nearest-neighbor antiferromagnetic interaction. For
finite chain lengthes or nonzero magnetization, there are nonzero spin Drude
weights and thus ballistic quantum spin transport can be achieved along the
reconstructed edges, These could be used for quantum spin information transfer
and spintronic applications.
