Magnetic properties of model non-carbon nanotubes with macroscopic value of ground state spin

The spin model of “ferrimagnetic” nanotube is proposed and some theoretical predictions concerning the ground state and low energy excitations of the model are given. In particular, the spin-wave structure of the exact ground state of bipartite magnets is proven. For tubes formed by weakly interacted cyclic fragments we show: first, the existence of gapless excitations with decreasing total spin; and second, gapped excitations. This leads to an intermediate plateau in field dependence of tube magnetization. Numerical calculations show the strong effect of frustrations on the magnetization of anisotropic spin tubes at low temperatures which may lead to the creation of an additional fractional magnetization plateau.