Computational and experimental investigation of the crystal orientation control effect on the electric permittivity and magnetic permeability of multiferroic composite materials

In this paper, the effect of crystal orientation control through polarization and magnetization treatments on physical properties was computationally and experimentally investigated for polycrystalline multiferroic composite materials consisting of ferroelectric and ferromagnetic phases. In the calculations, asymptotic homogenization theory was employed for scale-bridging between macrostructures and microstructures. The microstructural crystal orientations were ideally arranged on the assumption that the domain switching was perfectly done in both phases by a combination of external electric and magnetic fields in the vertical or horizontal direction. The homogenized physical properties, especially the electric permittivity and magnetic permeability, were compared among various microstructures with differently controlled crystal orientations for a BaTiO3/CoFe2O4 composite material. The computation identified an upper limit of the effect of crystal orientation control on physical properties. On the other hand, we focused on a polarization and magnetization treatment process as a case study, and then experimentally verified the effect of crystal orientation control. Specifically, a BaTiO3/Ni0.5Zn0.5Fe2O4 composite material was prepared through a wet mixing, molding, and sintering process, and then, it was poled electrically in the vertical direction and magnetically in the horizontal direction. Physical property measurements indicated that the in-plane components of the electric permittivity and magnetic permeability were increased, and the out-of-plane components were decreased by the polarization and magnetization treatments. The experimental results were qualitatively consistent with the computational results.