Analytical modeling of demagnetizing effect in magnetoelectric ferrite/PZT/ferrite trilayers taking into account a mechanical coupling

TL;DR

This paper develops an analytical model to understand the demagnetizing effects in ferrite/PZT/ferrite magnetoelectric trilayers, incorporating mechanical coupling, to optimize the ME voltage response in layered composites.

Contribution

It introduces a quasi-static analytical model that accounts for demagnetizing factors and mechanical coupling in magnetoelectric trilayers, enhancing understanding and optimization.

Findings

Demagnetizing factors derived for interacting magnetic discs.

Mechanical coupling significantly influences ME voltage.

Optimization of ME voltage achieved through model insights.

Abstract

In this paper, we investigate the demagnetizing effect in ferrite/PZT/ferrite magnetoelectric (ME) trilayer composites consisting of commercial PZT discs bonded by epoxy layers to Ni-Co-Zn ferrite discs made by a reactive Spark Plasma Sintering (SPS) technique. ME voltage coefficients (transversal mode) were measured on ferrite/PZT/ferrite trilayer ME samples with different thicknesses or phase volume ratio in order to highlight the influence of the magnetic field penetration governed by these geometrical parameters. Experimental ME coefficients and voltages were compared to analytical calculations using a quasi-static model. Theoretical demagnetizing factors of two magnetic discs that interact together in parallel magnetic structures were derived from an analytical calculation based on a superposition method. These factors were introduced in ME voltage calculations which take account of the demagnetizing effect. To fit the experimental results, a mechanical coupling factor was also introduced in the theoretical formula. This reflects the differential strain that exists in the ferrite and PZT layers due to shear effects near the edge of the ME samples and within the bonding epoxy layers. From this study, an optimization in magnitude of the ME voltage is obtained. Lastly, an analytical calculation of demagnetizing effect was conducted for layered ME composites containing higher numbers of alternated layers (). The advantage of such a structure is then discussed.