Monte Carlo Study of the Composition Dependence of the Curie Temperature in Mixed Ising Systems

The composition dependence of the Curie temperature in mixed Ising systems with different coupling constants has been studied by means of Monte Carlo numerical simulations. The results obtained are useful to get a better understanding of the deviations from Vegard's law observed in mixed ferroelectric-ferroelectric solid solutions. Deviations from linearity are obtained for non-homogeneous mixed solutions of Ising systems with coupling constants J_a and J_b and with a coupling constant among the two species J_ab different from (J_a+ J_b)/2. Two cases are studied: (a) J_ab > (J_a+ J_b)/2 (critical temperature above the linear interpolation) and (b) J_ab < (J_a+ J_b)/2 (critical temperature below the linear interpolation).

Keywords:

• Mixed systems
• Curie temperature
• Monte Carlo simulations

Acknowledgments

Paper originally presented at IMF-11, Iguassu Falls, Brazil, September 5–9, 2005; received for publication January 26, 2006.