Attempts to obtain BaTiO3/Fe2O3 core-shell type structures: The role of iron oxide nanoparticle formation and agglomeration

The manuscript shows the studies of structural and magnetic properties of BaTiO3/Fe2O3 samples prepared using five different chemical routes. We show that the undertaken processes leaded to the decoration of BaTiO3 grains with hematite nanoparticles, but not to a creation of a well-defined core-shell structure. These studies revealed that a strong tendency of the iron-oxide nanoparticles to form agglomerates, significantly reduces the possibility of a continuous shell formation around the core, and at the same time it promotes inter-particle interactions between magnetic nanoparticles. A detailed analysis of the results obtained in the structural and magnetic studies, allowed to state that magnetic properties of these composites are dominated by the properties of fine iron-oxide nanopowder. The collected isothermal magnetization curves clearly indicate the canted antiferro-magnetic properties characteristic for hematite, while the ac magnetization results exhibit the collective freezing process to the cluster glass like state (characteristic for interacting system of magnetic nanoparticles). This work provides detailed studies of systems prepared under different conditions and methods, which can serve as an important step towards obtaining well defined BaTiO3/Fe2O3 core-shell structures.