  The effect of opposite sign of interactions in a single-walled Ising nanotube
is investigated using the Wang-Landau algorithm. The thermodynamic observables
are calculated from the estimated density of states (DOS) with and without the
presence of an external magnetic field. Irrespective of the applied magnetic
field, a symmetric trend of DOS is observed for opposite sign of interactions
which is in contrast to the asymmetric trend for same sign of interactions.
Further, two types of anti-ferromagnetic (AFM) orderings, namely A-type and
C-type anti-ferromagnetic order, are observed for opposite sign of
interactions. These AFM spin orientations are switched to ferromagnetic (FM)
phase by increasing the applied magnetic field ($B$). However, the spin
ordering changes from the ordered AFM/FM phase to a disordered paramagnetic
phase by increasing the temperature. Phase diagram shows that these three
phases coexist around $B=2.0$. This study indicates that, by properly tuning
the magnetic properties, the single-walled nanotube can be used for fabrication
of new types of magnetic storage nano materials.
