Magnetoelectric coupling and strain transfer process in ferroelectric-ferrimagnetic magnetoelectric composite

We have adopted a new material design strategy, wherein we exploit some of the merits of additive assisted sintering and developed a particulate multiferroic composite with a microstructure that is conducive for good ME coupling between the ferroelectric and ferromagnetic phases. We have used a pseudo ternary multi-cation ferroelectric alloy system BiFeO3-PbTiO3-DyFeO3, sintered using MnO2 as an additive in optimized conditions resulted in the spontaneous precipitation of dysprosium-iron-garnet (DIG) phase from the matrix. We show that despite low volume fraction (~6%) of the DIG grains it resulted in a substantially enhanced switching of the ferroelectric domains under an applied magnetic field, causing ~ 40 % increase in the ferroelectric polarization under a modest magnetic field of 1 Tesla and large magnetoelectric voltage coefficient ~ 2500 mV/cm-Oe at the electromechanical resonance. This new strategy of synthesizing multiferroic system in situ via additive assisted sintering appears to be promising for producing self-grown particulate bulk multiferroic ceramic composites with a microstructure that benefits in efficient strain transfer between the piezoelectric and the ferromagnetic grains. We also demonstrated the synthesized multiferroic composite system can be taken as model system for the purpose of investigating an interesting question "how local stimuli within the interior of the system would make the ferroelectric system respond on the global scale?" The magnetostriction measurement revealed no measurable magnetostrain in the unpoled state of the specimen. Once it is electrically poled, a strain of ~ -4 ppm was observed at ~1 kOe. The phenomenon confirms that electrically poled ferroelectric matrix acts as an amplifier of the magnetic field-driven insignificant deformations induced in embedded ferrimagnetic islands. Our experiments validate that the sole contributor to the magnetic field-induced macroscopic measured strain is caused by a slight rearrangement of the aligned ferroelectric-ferroelastic domains by localized stress exerted by the isolated FM islands.