Navegando por Autor "Alves, T. F. A."
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Artigo Critical behavior of the 2D Ising model modulated by the Octonacci sequence(IOP Publishing, 2017) Alves, G. A.; Vasconcelos, Manoel Silva de; Alves, T. F. A.We investigated the Ising model on a square lattice with ferro and antiferromagnetic interactions modulated by the quasiperiodic Octonacci sequence in both directions of the lattice. We have applied the replica exchange Monte Carlo (parallel tempering) technique to calculate the thermodynamic quantities of the system. We obtained the order parameter, the associated magnetic susceptibility (χ) and the specific heat $(c)$ in order to characterize the universality class of the phase transition. Also, we use the finite size scaling method to obtain the critical temperature of the system and the critical exponents β, γ and ν. In the low temperature limit we have obtained a continuous transition with critical temperature around $T_{\rm c} \approx 1.413$ . The system obeys the Ising universality class with logarithmic corrections. We found estimatives for the correction exponents $\hat{\beta}$ , $\hat{\gamma}$ and $\hat{\lambda}$ by using the finite size scaling techniqueArtigo Critical properties of a two-dimensional Ising magnet with quasiperiodic interactions(American Physical Society, 2016) Alves, G. A.; Vasconcelos, Manoel Silva de; Alves, T. F. A.We address the study of quasiperiodic interactions on a square lattice by using an Ising model with ferromagnetic and antiferromagnetic exchange interactions following a quasiperiodic Fibonacci sequence in both directions of a square lattice. We applied the Monte Carlo method, together with the Metropolis algorithm, to calculate the thermodynamic quantities of the system. We obtained the Edwards–Anderson order parameter qEA, the magnetic susceptibility χ, and the specific heat c in order to characterize the universality class of the phase transition. We also use the finite size scaling method to obtain the critical temperature of the system and the critical exponents β, γ , and ν. In the low-temperature limit we obtained a spin-glass phase with critical temperature around Tc ≈ 2.274, and the critical exponents β, γ , and ν, indicating that the quasiperiodic order induces a change in the universality class of the system. Also, we discovered a spin-glass ordering in a two-dimensional system which is rare and, as far as we know, the unique example is an under-frustrated Ising model