Electromagnetic properties of multiferroic magnetoelectric BaTiO ₃-Co _xFe _3-xO ₄ core-shell particles obtained by homogeneous coprecipitation

Electromagnetic properties of multiferroic magnetoelectric core-shell structured BaTiO ₃-Co _xFe _3-xO ₄ composite particles synthesized by homogeneous coprecipitation method were studied. The complex permeability and permittivity of samples prepared with different R values (the molar ratio of FeCl ₂·4H ₂O to CoCl ₂·6H ₂O, M(FeCl ₂·4H ₂O)/M(CoCl ₂·6 H ₂O)) during the coprecipitation processes were measured in the frequency range of 2-8 GHz by a network vector analyzer. The result showed that the electromagnetic parameters of BaTiO ₃-Co _xFe _3-xO ₄ core-shell particles could be controlled effectively by adjusting the R value of reaction solution. The increasing R value intensified the interfacial polarization process, leading the ε′ value of BaTiO ₃-Co _xFe _3-xO ₄ core-shell particles to increase and the fluctuation of ε″ curves to become obvious. Meanwhile, the increasing R value enhanced M _s and adjusted the direction of easy magnetization axis, which resulted in the μ′ value of BaTiO ₃-Co _xFe _3-xO ₄ core-shell particles getting increased and the resonance peak of μ″ moving to a higher frequency. The increased complex permeability and permittivity also resulted in an improvement of dielectric and magnetic loss. Crown