title: Multicritical behavior of two coupled Ising models in the presence of a random field.
abstract: A system defined by two coupled Ising models, with a bimodal random field acting in one of them, is investigated. The interactions among variables of each Ising system are infinite ranged, a limit where mean field becomes exact. This model is studied at zero temperature, as well as for finite temperatures, representing physical situations which are appropriate for describing real systems, such as plastic crystals. A very rich critical behavior is found, depending directly on the particular choices of the temperature, couplings, and random-field strengths. Phase diagrams exhibiting ordered, partially ordered, and disordered phases are analyzed, showing the sequence of transitions through all these phases, similarly to what occurs in plastic crystals. Due to the wide variety of critical phenomena presented by the model, its usefulness for describing critical behavior in other substances is also expected.
authors.affiliation: Departamento de Física, Universidade Federal do Amazonas, 3000, Japiim 69077-000, Manaus-AM, Brazil.
authors.forename: Octavio D Rodriguez
authors.initials: OD
authors.lastname: Salmon
authors.affiliation: Centro Brasileiro de Pesquisas Físicas and National Institute of Science and Technology for Complex Systems, Rua Xavier Sigaud 150 22290-180, Rio de Janeiro-RJ, Brazil.
authors.forename: Fernando D
authors.initials: FD
authors.lastname: Nobre
mesh_terms: D003460:Crystallization; D008962:Models, Theoretical; D044367:Phase Transition; D010969:Plastics; D013696:Temperature
chemical_list: D010969:Plastics