The magnetoelectric (ME) effect is defined as the induced electric polarization of a material in an applied magnetic field, or the induced magnetization of the material in an applied electric field. The ME effect is naturally occurring in single phase crystals such as antiferromagnetic Cr2O3, and can also be artificially realized through layered piezoelectric and piezomagnetic composites. This study is interested solely in the artificial ME effect realized via the mechanical interaction of piezoelectric and piezomagnetic composites. There have been several experimental and theoretical studies on magnetoelectric materials for a half century; however there remains a lack of accurate theoretical models to properly describe the media. The lack of accurate theoretical models creates limitations in accurate understanding of the material through numerical solutions. This lack of accurate models as well as small ME coefficients achieved so far are some of the reasons why after many years of research into magnetoelectric materials, few applications exist.
Here, we introduce accurate and robust theoretical models that describe the effective material parameters for the longitudinal, transverse and in-plane magnetoelectric configurations. The models characterize the composite in terms of its constitutive equations, in which the electric and magnetic fields are coupled. We show that the theoretical model obtained closely approximates results obtained from experimental measurements of the ME composite. Comparison to previous theoretical models found in the literature shows that the current model better approximates the ME effect at points where the effect is greatest.
The theoretical model applies fundamental electromagnetic boundary conditions to fields obtained via the mechanical interaction of piezoelectric and piezomagnetic layers, under magnetic and electric field bias. Solutions to the electrical-mechanical and mechanical-magnetic interaction of the films results in the theoretical model. This model also takes into account the effects of an imperfect interface coupling that may exist between the layered composites by means of a parameter k whose values are between “0≤k≤1” The part of the study is completed with analyses of the different material combinations and the strength of the magnetoelectric effect possible.
Theoretical investigations into the electromagnetic propagation phenomena in magnetoelectric composites are carried out as well. Electromagnetic wave propagation is analyzed for the longitudinal, transverse, and in-plane ME configurations. This involves analytical solutions to the magnetoelectric wave equation. The magnetoelectric wave equation is derived analytically using Maxwell’s equations, and solutions are constructed to gain insight on the electromagnetic wave propagation characteristics. The polarizations of the propagating electromagnetic waves, modes of propagation, and direct effect of the magnetoelectric coupling terms on the behavior of the electromagnetic waves are identified.