The influence of interplanar coupling on the entropy and specific heat of the bilayer ferromagnet

► Pair Approximation is applied to study the S=1/2 magnetic bilayer. ► Anisotropic Heisenberg intraplanar and interplanar couplings are taken into account. ► Thermal behaviour of entropy, specific heat and isothermal entropy change is studied. ► Ising bilayer results are compared with Exact Diagonalization of Finite Clusters. ► A double peak behaviour of specific heat and isothermal entropy change is found.