Phase diagrams of a transverse Ising bilayer system

Critical properties of a spin-1/2 transverse Ising bilayer system consistin g of two different ferroelectric slabs with a same thickness L are studied on the basis of the two theoretical frameworks of the differential operator technique, namely the effective-field theory and the decoupling approximat ion, superior to the Bethe-Peierls approximation. We find some unexpected p henomena in the phase diagrams with L=1, such as the reentrant phenomenon ( or the reduction to zero of the critical temperature in an abnormal form), due to the competition of the interslab interaction and the transverse fiel d. They can be obtained from both the approximations and seem to be indepen dent of the theoretical approximation. (C) 2000 Elsevier Science B.V. All r ights reserved.