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Douglas F. de Albuquerque

Publications and source records attributed to Douglas F. de Albuquerque.

6 recordsLinked to original sources
arXiv2014

Mixed-bond spin-1 Ising model with nonlinear interactions for the Fe-Mn alloys

In this letter, we apply the mixed-bond spin-1 Ising model to the study of the magnetic properties of Fe-Mn alloys in the $α$ phase by employing the effective field theory (EFT). Here, we suggest a new approach to the ferromagnetic coupling between nearest neighbours Fe-Fe that depends on the ratio between the Mn-Mn coupling and Fe-Mn coupling and of second power of the Mn concentration $q$ in contrast with linear dependence proposed in the other papers. Also, we propose a new probability distribution for binary alloys with mixed-bonds based on the distribution for ternary alloys and we obtain a very good agreement for all considered values of $q$ in $T-q$ plane, in particular for $q>0.11$.

cond-mat.dis-nn↗
arXiv2014

Representation for the Pyrochlore Lattice

This work aims to present a representation for the Kagomé and pyrochlore lattices for Monte Carlo simulation and some results of the critical properties. These geometric frustrated lattices are composed of corner sharing triangles and tetrahedrons respectively. The simulation was performed with the Cluster Wollf Algorithm for the spins updates using the standard ferromagnetic Ising Model. The determination of the critical temperature and exponents was done through the Histogram Technique and the Finite-Size Scalling Theory.

cond-mat.dis-nn↗
arXiv2011

Study of the first-order phase transition in the classical and quantum random field Heisenberg model on a simple cubic lattice

The phase diagram of the Heisenberg ferromagnetic model in the presence of a magnetic random field (we have used bimodal distribution) of spin S=1/2 (quantum case) and $S=\infty $ (classical case) on a simple cubic lattice is studied within the framework of the effective-field theory in finite cluster (we have chosen N=2 spins). Integrating out the part of order parameter (equation of state), we obtained an effective Landau expansion for the free energy written in terms of the order parameter $Ψ(m)$. Using Maxwell construction we have obtained the phase diagram in the $T-H$ plane for all interval of field. The first-order transition temperature is calculated by the discontinuity of the magnetization at $T_{c}^{\ast}(H)$, on the other hand in the continuous transition the magnetization is null at $T=T_{c}(H)$. At null temperature (T=0) we have found the \textbf{coexistence} field $H_{c}=3.23J$ that is independent of spin value. The transition temperature $T_{c}(H)$ for the classical case ($S=\infty $), in the $T-H$ plane, is larger than the quantum case (S=1/2).

cond-mat.stat-mech↗
arXiv2010

Phase Diagram of mixed bond Ising systems by use of Monte Carlo and the effective-field theory

The phase transition of a random mixed-bond Ising ferromagnet on a cubic lattice model is studied both numerically and analytically. In this work, we use the Cluster algorithms of Wolff and Glauber to simulate the dynamics of the system. We obtained the thermodynamic quantities such as magnetization, susceptibility, and specific heat. Our results were compared with those obtained using a new technique in effective field theory that employs similar probability distribution within the framework of two-site clusters

cond-mat.dis-nn↗
arXiv2002

Heisenberg model in a random field: phase diagram and tricritical behavior

By using the differential operator technique and the effective field theory scheme we study the tricritical behavior of Heisenberg classical model of spin-1/2 in a random field. The phase diagram in the T-h plane on a square and simple cubic lattice for a cluster with two spins is obtained when the random field is bimodal distributed.

cond-mat.stat-mech↗