Synthesis and characterization of novel CoFe2O4-BaTiO3 multiferroic core-shell-type nanostructures

Novel multiferroic nanostructures of cobalt ferrite-barium titanate were synthesized by a two-step wet chemical procedure, combining co-precipitation and sol-gel techniques. The fraction of cobalt ferrite in the nanostructures was varied from 20 to 60 wt.%. X-ray diffraction confirmed the presence of both the spinel and the perovskite phases, with average crystallite sizes in the range of 15-28 nm. Both the degree of tetragonality of barium titanate and the lattice parameter of cobalt ferrite significantly increased with the content of ferrite in the nanostructures, revealing a crystallographic distortion related to the shell thickness. Transmission electron microscopy data showed two-phase composite nanostructures consisting of a cobalt ferrite core surrounded by a barium titanate shell-like coating. Magnetization data showed expected ferromagnetic behavior. The multifierroic nanostructures are proposed as building blocks for higher-order multiferroic inorganic and hybrid inorganic-organic nanocomposites. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.