Microstructure and magnetoresistance driven magnetocapacitance in ex-situ combustion derived BaTiO3-CoFe2O4 bulk magnetodielectric composites

Enhanced magnetodielectric properties including magnetocapacitance have been observed in the BaTiO3CoFe2O4 composites due to the microstructural interactions between the dielectric and magnetic phases. Based on this concept, this research work explores the frequency and field dependent magnetocapacitance and magnetoresistance of 70 wt% BaTiO3 - 30 wt% CoFe2O4 composites. Ex-situ synthesis method is adopted to form a partial 0-3 microstructure and this composite is sintered at 900 degrees C and 1000 degrees C. Phases such as pseudo-cubic BaTiO3 and cubic CoFe2O4 have been observed in both composites. Secondary phase of barium hexaferrite is observed at 1000 degrees C. Based on FESEM, CoFe2O4 phase is found to be embedded in the BaTiO3 matrix at 900 degrees C, however interconnected CoFe2O4 along with partially shrunk BaTiO3 has been observed at 1000 degrees C. The permittivity of composite is found to be - 317 and - 451 at 900 degrees C and 1000 degrees C, respectively, and the MaxwellWagner polarization is tuned by the microstructure. The effect of space charge is found to be relatively larger at 1000 degrees C. Magnetic nature is altered due to the connectivity of ferrite phases. Magnetocapacitance values are mostly analogues to the magnetoresistance behavior in both composites. The percentage of magnetocapacitance is found to be increased nearly 5 times due to the microstructural variations. Field and frequency-dependent magnetocapacitance responses along with Cole-Cole plots of composite confirmed the role of microstructural interactions and magnetoresistance.

Automated summary

Enhanced magnetodielectric properties, including magnetocapacitance, are observed in BaTiO3CoFe2O4 composites. The microstructural interactions between the dielectric and magnetic phases play a crucial role. The magnetocapacitance and magnetoresistance of the composites were studied, and it was found that the magnetocapacitance increased nearly 5 times due to microstructural variations. Field and frequency-dependent magnetocapacitance responses confirmed the importance of microstructural interactions and magnetoresistance.