Role of the Dipolar Interaction in Single-Walled Ferromagnetic Nanotubes: Monte Carlo Study

Abstract

This document presents a study of the influence of the dipolar interactions and geometrical parameters on the magnetic properties of single-walled ferromagnetic nanotubes built by using square and hexagonal unit cells. For this study, a Hamiltonian, which includes dipolar interactions and nearest neighbor classical Heisenberg model, was used; furthermore, the Monte Carlo method combined with the Metropolis algorithm was used to determine the observables required. The analyses were focused on the magnetization per magnetic site and the critical temperature that was obtained by using specific heat peaks. These properties were calculated varying the length, diameter, boundary conditions, dipolar parameter and unit cell type. It was observed that the system showed different behaviors depending on the use of periodic or free boundary conditions; moreover, there is a strong influence of the unit cell type on the magnetic properties, caused by the difference of the number coordination between them. For both cases, square and hexagonal unit cells, the critical temperature increased as the nanotube length was increased; nevertheless, the diameter produced an inverse effect. On the other hand, the dipolar interaction always generated an increase in the critical temperature. This behavior allows us to conclude that longrange dipolar interactions have a strong effect on the magnetic properties of the single-walled magnetic nanotubes.