title: Phase diagrams of a spin-1 Ising system with competing short- and long-range interactions.
abstract: We have studied the phase diagrams of the one-dimensional spin-1 Blume-Capel model with anisotropy constant D, in which equivalent-neighbor ferromagnetic interactions of strength -J are superimposed on nearest-neighbor antiferromagnetic interactions of strength K. A rich critical behavior is found due to the competing interactions. At zero temperature two ordered phases exist in the D/J-K/J plane, namely the ferromagnetic (F) and the antiferromagnetic one (AF). For lower values of D/J(D/J<0.25) these two ordered phases are separated by the point K_{c}=0.25J. For 0.25<D/J≤0.50, the paramagnetic phase P emerges in a region separated between the lines determined by D/J=0.5-K/J and D/J=K/J. For D/J>0.5, only phases AF and F exist and are separated by a line given by D/J=K/J. At finite temperatures, we found that the ferromagnetic region of the phase diagram in the k_{B}T/J-D/J plane is enriched by another ferromagnetic phase F^{^{'}} above a first-order line for 0.195<K/J<0.250. This first-order line, which separates phases F and F^{^{'}}, begins at a coexistence point, where phases F,F^{^{'}}, and P coexist, and ends at an ordered critical point. Similarly, we found that the phase F^{^{'}} is present in the phase diagram in the k_{B}T/J-K/J plane for 0.228<D/J<0.286.
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: Departamento de Física, Universidade Federal do Amazonas, 3000, Japiim, 69077-000, Manaus-AM, Brazil and National Institute of Science and Technology for Complex Systems, 3000, Japiim, 69077-000, Manaus-AM, Brazil.
authors.forename: J Ricardo
authors.initials: JR
authors.lastname: de Sousa
authors.affiliation: Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-000, Manaus-AM, Brazil.
authors.forename: Minos A
authors.initials: MA
authors.lastname: Neto