Exchange bias mediated self-biased magnetoelectric coupling in Co–BaTiO3 composites

Abstract

The magnetoelectric composites constituted by ferromagnetic cobalt (Co) fillers having various morphologies and ferroelectric BaTiO₃ (BTO) were successfully synthesized. For the investigated Co–BTO multiferroic system, an unusual magnetic phenomenon called exchange bias was observed. The several phase transitions of BTO are observable in the thermomagnetic data, which signify the magnetoelectric coupling between Co and BTO. The largest values of multiferroic coupling coefficients noticed for the Co–BTO composites having Co-particle and Co-chain inclusions are 20.34 mV cm⁻¹ Oe⁻¹ and 19.43 mV cm⁻¹ Oe⁻¹, respectively; these values are greater than the formerly reported values for the Co–BTO multiferroic composite. Interestingly, the studied composites display exchange bias assisted direct magnetoelectric coupling. Hence, the developed Co–BTO magnetoelectric systems have the potential for device applications such as switches, sensors, actuators and random access memories. The density functional theory based theoretical modelling further enabled us to understand how the electronic structure of an ideal Co–BTO composite is influenced by the change in BTO concentration.