Magnetic phases in Ising square lattices with mixed bonds

CuO2 planes are modeled by means of a square lattice with antiferromagnetic coupling provided by the oxygen between two copper ions and ferromagnetic coupling when the oxygen is absent. The magnetic interaction is described using an Ising Hamiltonian with interacting first-nearest neighbors. The ferromagnetic exchange interaction is supposed to be larger than the antiferromagnetic one. A Monte Carlo routine is then defined in order to minimize the energy and to calculate physical parameters such as correlation to nearest neighbors, time correlation to the same site, and a schematic of a phase diagram.