Some characteristic properties of initial susceptibility in a Ising nanotube

Initial susceptibility and magnetization of a cylindrical nanotube described by the Ising model are investigated by the use of the effective field theory with correlations (EFT), since the phase diagrams of the system have been examined in the previous work of Kaneyoshi (2010) [8] using the two theoretical frameworks of the mean field theory and the EFT. The effects of the two exchange couplings at the surface shell and in the core to the initial susceptibility are clarified. Some characteristic phenomena are found in the thermal variations, depending on the ratios of the physical parameters in the surface shell and the core. It is also discussed whether the Neel hyperbola in the paramagnetic region is valid for a nano-scaled ferrimagnetic system.

Research highlights
► A variety of characteristic phenomena may be obtained in the initial susceptibility of the Ising nanotube.
► We have found that the coefficient A in the paramagnetic susceptibility defined by 1/x=A(T/TC−1) may exhibit some peculiar behaviors, depending on the values of exchange interactions.
► It is also proved that the Neel hyperbola can be applicable for a ferrimagnetic Ising nanotube in the paramagnetic region, even when the effective-field theory better than the MFA is applied.