| Organic-inorganic composites have received great research attention across the fields of polymeric chemistry, physical chemistry, organic chemistry and materials chemistry, because they combine the merits of the inorganic materials and the organic polymers. It is exhibiting the good mechanical, optical, electrical, magnetic properties. Aniline and its derivatives (o/m-Toluidine etc) have been extensively studied due to their adjustable conductivity, good stability and relatively easy preparation. Conducting polymer composites have become active in the field of organic-inorganic composites. And more over, the ferrite particles coated by polymer can reduce the agglomeration in some extent. Owing to its fairly large magnetocrystalline anisotropy, high Curie temperature, relatively large magnetization and excellent chemical stability, Barium ferrite recently has been extensively studied for advanced telecommunication and microwave devices.In this article, the conducting and magnetic Poly(o-toluidine)-Ba ferrite, Poly(m-toluidine)-Ba ferrite, Poly(o-toluidine-co-aniline)-Ba ferrite and Poly(m-toluidine-co-aniline)-Ba ferrite composites with different Ba ferrite content were synthesized by in-situ aqueous polymerization using hydrochloric acid as dopant, ammonium peroxydisulfate as oxidant.The structure of samples was characterized by Fourier transform infrared spectra (FT-IR), UV-Vis spectra and X-ray diffraction (XRD). The particle sizes and morphologies of samples were observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The thermal stability of samples was measured by thermogravimetric analysis (TG-DTA).XRD analysis revealed that the composites were composed of the conducting polymer and ferrite particles, and incorporation of ferrite particles had the influence on the crystallinity of conducting polymer. The results of spectroanalysis confirmed that there was interaction between ferrite particles and polymer chains. The bonding interaction between ferrite particles and polymer chains in the composites had been studied as well. The results of TEM and SEM indicated that the ferrite particles were the well wrapping of ferrite particles with polymers in the composites and formed core-shell structure clearly. TG-DTA revealed that the incorporation of ferrite improved the thermal stability of composites.Conductivity of samples was measured by the four-point probe technique. The magnetic properties of composites were measured at room temperature under applied magnetic field by using a vibrating sample magnetometer (VSM). The results indicated that the incorporation of ferrite particles had an effect on the crystallinity and degree of doping in the conducting polymer, leading to decreasing the consecution, ordered and degree of conjugation in the conducting polymer. Due to the non-magnetic polymer contribution to the total magnetization, the magnetization of composites were lower than that of pure ferrite under applied magnetic field, and decreased with increasing the content of conducting polymer. In the polymerization process, the polymer was deposited on the ferrite surface and crystallite boundary, which leads to a decrease in magnetic surface anisotropy of ferrite particles, consequently, the coercivity of composites decreased.In addition, the microwave electromagnetic parameters (complex permeability and complex permittivity) of composites were measured by a Materials/Impendence analyzer in the 1 GHz～3 GHz ranges. The results showed that the decrease in real part (μ') and imaginary part (μ") of complex permeability was related to the volume fraction of ferrite particles. And the real part (ε') and imaginary part (ε") of complex permittivity as a function of the kinds and contents of polymer, we also studied the influence with permeability by temperature of reactions.
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