Structure and magnetic properties of the Co_1-xNi_xFe₂O₄-BaTiO₃ core-shell nanoparticles

Highlights: • Core-shell Co_1-xNi_xFe₂O₄-BaTiO₃ composites were synthesized by soft chemical routes. • Anomalous magnetic behavior was found for x = 0.2 to 0.6 composites. • Magnetic core behaviors very different from those of the composites. - Abstract: Core-shell Co_1-xNi_xFe₂O₄-BaTiO₃ (0 ≤ x ≤ 1) composite nanoparticles were synthetized by a combination of soft chemical routes such as co-precipitation and sol gel. X-ray diffraction patterns confirm the presence of both the materials, the ferrite solid solution, and BaTiO₃. Unit cell parameters become smaller as Ni concentration is increased. SEM and HRTEM micrographs corroborate the formation of core-shell nanostructures. Magnetic behaviors of the core are very different from those of the composites. Anomalous magnetic behavior of the composite nanostructures have been discussed considering a coupling between the ferromagnetic and ferroelectric phases. Present work provides an experimental evidence of complex behaviors in magnetoelectric composites and strengthens the idea of remarkable changes of the magnetoelectric properties depending on the nanostructures, morphology or the method of synthesis.