Microstructure Induced Tunable Magnetocapacitance Response of Barium Titanate- Ferrite Composite Systems

Abstract

Magnetic and dielectric properties exhibited by magneto-dielectric composite systems can be tunable using electrical and magnetic fields due to mechanical coupling effect, which may led to potential application such as electrically readable magnetic memories, phase shifters, miniature antennas and magnetic sensors. The mechanical coupling effect strongly depends on morphology of the phases (magnetic and dielectric) present in the composites along with their orientation and interaction, which can be altered by using a novel auto-combustion derived ex-situ synthesis technique. The prime objective of this research work was to tailor the microstructure as well as tune the magnetocapacitance, an important property of the magnetodielectric composite. In the above synthesis technique, the calcined powder (derived via autocombustion) of one phase of composite was added in the solution of other phase and combusted. In this research work, magneto – dielectric composite systems (30 wt % magnetic phase and 70 wt % dielectric phase) such as CoFe2O4 (CF)@BaTiO3 (BT); ZnFe2O4 (ZF)@BT and CoZnFe2O4 (CZF)@BT have been prepared. Similarly, same weight percentage composites with interchanged phases (BT@CF, BT@ZF and BT@CZF) have also been prepared using above technique. All composite powders were calcined and the pellets were sintered at 1150 °C. XRD confirms the presence of dielectric and magnetic phases in the composites. FESEM images revealed plate-like along with nearly spherical morphologies of BT and polyhedral morphology of ferrite phase. Plate-like morphology was prominent in ferrite@BT composites, but suppressed when the phases were interchanged (i.e. BT@ferrite). The microstructural variation in the above composites led to change the magnetocapacitance response in both positive and negative directions, which is one of the novelty in the present composite systems. Further, magnetocapacitance response was analyzed using magnetoimpedance results along with the help of Cole-Cole plots.