Hysteresis loops of ferroelectric bilayers and superlattices

A ferroelectric superlattice with an antiferroelectric interfacial coupling is considered; the same model describes a bilayer with antiferroelectric c oupling. By mapping minimum points in the Landau free energy expression and plotting them against the applied electric field, a triple hysteresis loop pattern is obtained. The loop patterns vary between typically ferroelectri c and typically antiferroelectric depending on the layer thicknesses and th e magnitude of the interfacial-coupling constant. This work suggests the po ssibility of designing multilayer elements for computer memories with four or more different storage states. (C) 2000 American Institute of Physics. [ S0003-6951(00)03843-2].