Compositional dependence of the Curie temperature in mixed ferroelectrics: effective field approach

An effective field approach is used to investigate the compositon depedence of the Curie temperature T_C(x) for mixed ferroelectric systems of partially deuterated triglycine sulfate (TGS)_1−x(DTGS)_x, and partially deuterated triglycine selenate (TGSe)_1−x(DTGSe)_x. We found that the coupling strength between the two sub systems is weaker than the average value of the effective field within each system, this can account for the non-linearity of composition dependence of the Curie temperature in these mixed ferroelectric systems.