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Uncovering the secrets of the 2D random-bond Blume-Capel model

2010    Malakis, A.; Berker, A. Nihat; Hadjiagapiou, I. A.; Fytas, N. G.; Papakonstantinou, T.

The effects of bond randomness on the ground-state structure, phase diagram and critical behavior of the square lattice ferromagnetic Blume-Capel (BC) model are discussed. The calculation of ground states at strong disorder and large values of the crystal field is carried out by mapping the system onto a network and we search for a minimum cut by a maximum flow method. At finite temperatures the system is studied by an efficient two-stage Wang-Landau (WL) method for several values of the crystal field, including both the first- and second-order phase transition regimes of the pure model. We attempt to explain the enhancement of ferromagnetic order and we discuss the critical behavior of the random-bond model. Our results provide evidence for a strong violation of universality along the second-order phase transition line of the random-bond version. (C) 2010 Elsevier B.V. All rights reserved.