Interfacial bonding effect on nonlinear magnetoelectric response of multiferroic composites

Magnetoelectric materials incorporate both ferroelectric and ferromagnetic phases to induce giant magneto electric coupling effect, which is one of the most important features and absent in either ferromagnetic or ferroelectric materials alone. ME effects is achieved through elastic deformation between the ferromagnetic and ferroelectric phases. It also depends on the constituent phase properties, the volume concentration and the interfacial conditions. In this paper, we investigate the interfacial effects on the nonlinear ME response of the multiferroic composites consisting both ferromagnetic and ferroelectric through epoxy bonding by using a unified micromechanics model. First, the nonlinear coupling behaviors of each individual ferromagnetic or ferroelectric phase are studied by consideration of evolution of the microstructure due to domain switching. Then, the coated or bonded inclusions are treated as a two-phase composite and a homogenization approach is applied to obtain the equivalent properties of the homogenized coated inclusions. Finally, the micromechanics approach is applied again to investigate the overall effective coupling properties of the multiferroic composites consisting coated inclusions and matrix. With a focus on the Terfenol-D/PZT/Terfenol-D system, we demonstrate how its coupling coefficients alpha(33), and voltage coefficient alpha(E33) depend on the interfacial bonding. Comparisons between the theoretical calculations and the existing experimental data agree well.