Enhancement of remanence ratio and coercivity in nanostructured CoFe2O4- poly(aniline) composites

BERHO, F. M.; ANTONEL, P. S.; JORGE, G. A.; MOLINA, F. V.

Buenos Aires

Congreso; X Latin American Workshop on Magnetism, Magnetic Materials and their Applications; 2013

In recent years there has been a growing interest in composites formed by magnetic nanoparticles embedded in a polymer matrix, particularly of conducting polymers. Among these materials, CoFe2O4-PANI composites have not received much attention in the literature; there are some recent reports which have synthesized the composite and measured its properties, however little attention was given to the analysis of the magnetic behaviour. Also, the possible eects of particle-matrix interactions on the composite properties are not well understood. In this work, CoFe2O4-PANI composites have been prepared by a wet chemical method, with in situ aniline polymerization in acid media. The ferrite nanoparticles were covered with poly(vinylpyrrolidone) (PVP) before polymerization attempting to protect them from the acid media employed. The composites were characterized by XRD studies, SEM and TEM observation, thermogravimetric analysis, conductivity measurements, IR spectroscopy and DC magnetization measurements. The magnetic behavior has been analyzed taking into account the magnetic interactions between particles and the possible participation of the polymer matrix. It was found that the PVP protection has shown to be partial, as the particles have a lower diameter in the composite, and as revealed in the IR results. The DC magnetization hysteresis loops show ferromagnetic behaviour for particles and composites. The remanence ratio increases as the polymer contents increases, the coercivity decreases rst and then increases, and the saturation magnetization does not follow the ferrite mass fraction in the composite. These results indicate the presence of interactions related to the amount of polymer present, which are not consistent with present models of magnetic dipolar interactions. It is proposed that an indirect exchange mechanism (RKKY-like) between the nanoparticles and PANI localized spins mediated by the conduction electrons is responsible for the observed magnetic behaviour.