Edge-state magnetism in hydrogenated armchair carbon nanotubes

We have investigated the antiferromagnetic edge states in hydrogenated carbon nanotubes by using the density functional theory calculations. The total energy difference between the antiferromagnetic and ferromagnetic states, corresponding to the exchange energy gain stabilizing the antiferromagnetic state, changes by an order of magnitude by controlling the hydrogen adsorption pattern and is nearly independent of the nanotube size for a properly chosen pattern, indicating that the antiferromagnetic edge states in the real size nanotubes can be realized at high temperatures. The coexisting zigzag and bearded edges in the hydrogenated CNTs are believed to enhance the exchange energy gain.