Engineering the Magnetoelectric Response in Piezocrystal-Based Magnetoelectrics: Basic Theory, Choice of Materials, Model Calculations

This chapter presents a theoretical basis of the anisotropic magnetoelectric (ME) effect in tri-layers of metglas and piezoelectric (PE) single crystals. The properties of various common PE and magnetostrictive substances are discussed, and arguments for the choice of the most appropriate materials are made. A linear description of the ME effects in terms of electric, magnetic and elastic material fields and material constants is presented. An averaging quasi-static method is used to illustrate the relation between the material constants, their anisotropy and the transversal direct ME voltage and charge coefficients. Subsequently, the aforementioned model is employed in the calculation of the maximum expected direct ME voltage coefficient for a series of tri-layered Metglas/Piezocrystal/Metglas composites as a function of the PE crystal orientation. The ME effects are shown to be strongly dependent on the crystal orientation, which supports the possibility of inducing large ME voltage coefficients in composites comprising lead-free PE single crystals such as LiNbO₃, LiTaO₃, α-GaPO₄, α-quartz, langatate and langasite through the optimization of the crystal orientation.