A self-consistent approach to the one-dimensional chain models for the ferro- and antiferro-magnetism of nanotubes

We employ a self-consistent simulation approach based on quantum theory to investigate the physical properties of a pair of ferromagnetic and antiferromagnetic nanotubes. It was observed that under the given conditions, no matter the external magnetic field was absent or applied along the easy longitudinal axis, the spins always ordered in that direction due to the special geometric shape of the tubes and the magnetic uniaxial anisotropy, so that the two sorts of nanosystems exhibit typical ferromagnetic and antiferromagnetic properties, which may find applications in modern technology, in strong contrast to the phenomena observed previously in nanoparticle, where an external magnetic field, applied parallel to the antiferromganetically coupled spins, is able to turn the spins off their original direction to form symmetric pattern around the field direction. This peculiar feature enable us to build up one-dimensional chain models for the two sorts of nanosystems. Considering their fast computational speed and simplicity, these theoretical models were then utilized to investigate the finite size effects of the nanosystems, and perform further analysis for long tubes. Especially, our results obtained with the theoretical models and the numerical approach are exactly identical, verifying the correctness and applicability of the computational methodology.