ABSTRACT
A series of difficulties peculiar to bulk composites can be overcome in layered structures. Giant magnetoelectric (ME) effects in layered composites are due to (i) high piezoelectric and piezomagnetic coefficients in individual layers, (ii) effective stress transfer between layers, (iii) ease of poling and subsequent achievement of a full piezoelectric effect, and (iv) ability to hold charge due to suppression of leakage currents across composites with a 2-2 connectivity. Prior theoretical models based on mechanics and constitutive relationships by Harshe et al. [6] were restricted to account for ME voltage coefficients in laminates having ideal mechanical connection at the interfaces between layers. Principal disadvantages of this earlier approach [6] were as follows: (i) For the case of longitudinally oriented fields, the effect of the magnetic permeability of the ferrite phase was ignored. Diminution of interior (local) magnetic fields results in a weakening of ME interactions via demagnetization fields. (ii) The case of fields applied in cross orientations to the ME layer connectivity was not considered, which later experimental investigations revealed large ME responses. And, (iii) imperfection of the mechanical connection between constituent phases was not considered.
