Phase diagram of an Ising model with long-range frustrating interactions: A theoretical analysis

We present a theoretical study of the phase diagram of a frustrated Ising m odel with nearest-neighbor ferromagnetic interactions and long-range (Coulo mbic) antiferromagnetic interactions. For nonzero frustration, long-range f erromagnetic order is forbidden, and the ground state of the system consist s of phases characterized by periodically modulated structures. At finite t emperatures, the phase diagram is calculated within the mean-field approxim ation. Below the transition line that separates the disordered and the orde red phases, the frustration-temperature phase diagram displays an infinite number of "flowers," each flower being made by an infinite number of modula ted phases generated by structure combination branching processes. The spec ificities introduced by the long-range nature of the frustrating interactio n and the limitation of the mean-field approach are finally discussed.