ABSTRACT
In this chapter, the author shows the results obtained by extensive Monte Carlo (MC) simulations and analytical Green’s function (GF) method for a thin film made of stacked triangular layers of atoms using the Heisenberg spin model. In addition, he shows from MC histogram calculation that the value of the ratio of critical exponents of the observed transitions is deviated from the values of two- and three-dimensional Ising universality classes. The frustration is known to cause a great number of striking effects in various bulk spin systems. Its effects have been extensively studied during the last three decades theoretically, experimentally and numerically. The guarantees the existence of a phase transition at finite temperature, since it is known that a strictly two-dimensional system with an isotropic non-Ising spin model (XY or Heisenberg model) does not have long-range ordering at finite temperature.
