Electromagnetic properties of multiferroic magnetoelectric BaTiO3-CoxFe3−xO4 core-shell particles obtained by homogeneous coprecipitation

► We studied electromagnetic properties of BaTiO3-CoxFe3−xO4 core-shell particles. ► The molar ratio of FeCl2·4H2O to CoCl2·6 H2O(R) controls electromagnetic parameters. ► Interfacial polarization adjusted by R affects ε′ value and the fluctuation of ε″. ► Ms enhanced by increasing R makes the μ′ increase with R value. ► Direction of easy magnetization axis adjusted by R affects the resonance peak of μ″.