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 multiferroic nanostructures are proposed as building blocks for higher-order multiferroic inorganic and hybrid inorganic–organic nanocomposites.