“…Even the theoretical study of these systems has its difficulties, considering that only a handful of them are exactly solvable [22]; we must therefore resort to approximation methods. For instance, spin-1/2, spin-1 and mixed-spin Ising bilayers have been studied within various approaches, such as the mean-field approximation (MFA) [23][24][25][26], the effective-field approximation (EFA) [27][28][29][30][31][32][33], renormalization group (RG) [24,34,35], transfer matrix (TM) [23,34,36], high-temperature series expansion [26], and Monte Carlo (MC) simulations [24,[37][38][39][40][41]. A cellular automata (CA) simulation method was also employed in the analysis of both spin-1/2 Ising and 3-states Potts model bilayers [42].…”