  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.
