Coercivity and exchange bias of bismuth ferrite nanoparticles isolated by polymer coating

Bismuth ferrite nanoparticles have been extensively investigated over the last few years due to their potential candidacy for application in future memory devices. However, all the work reported so far on bismuth ferrite nanoparticles is on agglomerated nanoparticles. Agglomerated particles can magnetically interact with each other. To utilize them for device application, it is useful to know the properties of the individual particles. Here, de-agglomeration of ∼75 nm bismuth ferrite nanoparticles is achieved by polyaniline coating on the surface. The structural and magnetic properties of agglomerated and de-agglomerated nanoparticles are compared. It is observed that there is a change in the lattice parameters and Fe-O-Fe and O-Bi-O bond angles due to polyaniline shell. The coercivity of the bismuth ferrite/polyaniline core shell particles is reduced as compared to pure and agglomerated bismuth ferrite particles. The observed changes in the magnetic properties of coated particles are attributed to the shell induced isolation of individual bismuth ferrite nanoparticles as well as structural changes due to polyaniline coating.