▎ 摘　　要

We present a density-functional-theory study of chromium-chain-embedded graphene and carbon nanotubes with a line defect consisting of octagonal and pentagonal carbon rings. It is shown that chromium atoms can be spontaneously adsorbed at octagonal sites and form an atomic chain along the line defect in graphene and carbon nanotubes. This chromium-chain-embedded line defect in carbon systems exhibits a local spin band gap and acts as a quasi-one-dimensional half-metallic wire. The half-metallicity results from the hybridization between d orbitals of the chromium atoms and p(z) orbitals of carbon atoms, which resembles the well-known p(z)-d Zener exchange-type mechanism. Moreover, the spin-dependent electronic properties in nanotubes can be controlled by the tube diameter. These results open a new route to explore spintronics in carbon-based nanodevices.