Nonmonotonic magnetic field dependence of remanent ferroelectric polarization in reduced-graphene-oxide-BiFeO$_3$ nanocomposite

TL;DR

This study reveals a nonmonotonic magnetic field dependence of remanent ferroelectric polarization in a reduced-graphene-oxide-BiFeO3 nanocomposite, highlighting interface-driven magnetoelectric coupling effects at room temperature.

Contribution

It demonstrates how interface reconstruction in graphene/BiFeO3 nanocomposites can tune magnetoelectric properties through nonmonotonic polarization behavior.

Findings

Remanent polarization varies nonmonotonically with magnetic field.

Fe-C bonds at interfaces influence magnetic and electronic structure.

Magnetoelectric coupling arises from competition between interface and bulk effects.

Abstract

In a nanocomposite of reduced graphene oxide (RGO) and BiFeO$_3$ (BFO), the remanent ferroelectric polarization is found to follow nonmonotonic magnetic field dependence at room temperature as the applied magnetic field is swept across 0-20 kOe on a pristine sample. The remanent ferroelectric polarization is determined both from direct electrical measurements on an assembly of nanoparticles and powder neutron diffraction patterns recorded under 0-20 kOe field. The nanosized ($\sim$20 nm) particles of BFO are anchored onto the graphene sheets of RGO via Fe-C bonds with concomitant rise in covalency in the Fe-O bonds. The field-dependent competition between the positive and negative magnetoelectric coupling arising from magnetostriction due to, respectively, interface and bulk magnetization appears to be giving rise to the observed nonmonotonic field dependence of polarization. The emergence of Fe-C bonds and consequent change in the magnetic and electronic structure of the interface region has influenced the coupling between ferroelectric and magnetic properties remarkably and thus creates a new way of tuning the magnetoelectric properties via reconstruction of interfaces in nanocomposites or heterostructures of graphene/single-phase-multiferroic systems.