Magnetoelectric Property Evaluation of Polycrystalline Multiferroic Composite Materials

Abstract

Multiferroic composite materials consist of ferroelectric and ferromagnetic phases. The interference between these two phases generate the ME effects. The ME effects strongly depend on inhomogeneous microstructure. In this paper, the generating mechanism of magnetoelectric (ME) effects was numerically investigated for polycrystalline multiferroic composite materials. A multiscale simulation based on asymptotic homogenized theory was employed for scale-bridging between macro and micro structures. Physical properties of ferroelectric (FE) and ferromagnetic (FM) were allocated to every element in micro FE model by using a random generator. The crystal orientations were arranged in consideration of domain switching system of both phases. The macrostructural physical homogenized properties were analyzed and the influence of volume fraction of FE phase were investigated. The microstructural strain distributions were investigated when an external magnetic field was applied to the macrostructure. The overall frequency distribution of microstructural strain exists in equilibrium. It has a center at zero and symmetry against positive and negative sides. However the strain distribution in only FE phase shifts to positive side, and that in FM phase shifts to negative side. It was found that the shift of microstructural strain distribution in each phase and macrostructural piezoelectric and piezomagnetic constants are dominate factors of ME effects. The combination of these factors creates the maximum peak of ME coefficients.