Hydrothermal synthesis and properties of NiFe 2O 4@BaTiO 3 composites with well-matched interface

Abstract

NiFe 2O 4@BaTiO 3 multiferroic composite particles were produced by a simple hydrothermal method in two steps: preparing NiFe 2O 4 nanoparticles and then synthesizing core-shell nanocomposites. Multiferroic composite ceramics were sintered from these powders. X-ray diffraction, Raman scattering and energy dispersive x-ray analyses indicated that the core-shell composites with a NiFe 2O 4 core and BaTiO 3 shell were formed in the hydrothermal environment. Different types of sharp interfaces were self-assembled owing to the minimization of direct elastic energy. The saturation magnetization of the composites linearly increased with the NiFe 2O 4 content while the dielectric constant decreased. A dielectric peak appeared at around 460°C because of the oxygen vacancies in the BaTiO 3 ceramics. It resulted in an enhancement of magnetic permeability in the composites, indicating magnetoelectric coupling that was also observed by direct magnetoelectric measurements. © 2012 National Institute for Materials Science.