Magnetic Properties of XXZ Heisenberg Antiferromagnetic and Ferrimagnetic Nanotubes

The spin-1/2 antiferromagnetic and spin-(1/2, 1) ferrimagnetic single-walled nanotubes are described by XXZ Heisenberg model. The sublattice magnetization and the critical temperature of the system are calculated by using the double-time spin Green’s function method. At zero temperature, with the increase of the exchange interaction in the circumferential direction, a maximum value appears in the sublattice magnetization curves of antiferromagnetic and ferrimagnetic systems. As the diameter of the tube increases, the spin quantum fluctuations and thermal fluctuations are suppressed. In addition, the spin quantum fluctuation of the spin-1/2 antiferromagnetic system is greater than that of the spin-(1/2, 1) ferrimagnetic system. The critical temperature of the system increases firstly and then tends to a constant with the increase of the diameter of tube, and it decreases to zero as the exchange anisotropy of the system disappears.