Synthesis, characterization, magnetic and electrical properties of the novel conductive and magnetic Polyaniline/MgFe2O4 nanocomposite having the core-shell structure

Conductive and magnetic Polyaniline/MgFe2O4 nanocomposite was successfully synthesized in the form of core-shell via in situ chemical polymerization of aniline in the presence of MgFe2O4 nano-particles. X-ray powder diffraction of ferrites indicated that the structure of the core material is having the spinel structure, and demonstrated the formation of PAni/MgFe2O4 nanocomposite. XRD and TEM photographs showed that the particle's size of the MgFe2O4 core-material were around 30-35 nm before coating with Polyaniline, and grown up to 45 nm in the core-shell nanocomposite after coating. Although PAni has a relatively smaller electrical field coefficient than the core-shell nanocomposite, the resistivity of the core-shell material decreased, and hence its conductivity increased after a certain threshold voltage of 0.98 V equivalent to threshold electric field value equals 5.5 V cm(-1). The magnetic hysteresis loops investigated with VSM indicated that coating MgFe2O4 with Polyaniline has an healing effect which covers the ferrite surface defects, thus decreasing the magnetic surface anisotropy of ferrite particles leading to a decrease of the saturated magnetization (Ms) from 21.33 emu/g to 5.905 emu/g and a decrease of the coercivity (Hc) from 88.66 Oe to 81.6 Oe for MgFe2O4 and the core-shell nanocomposite respectively due to the amount of Polyaniline added. TGA and DTA revealed improved thermal stability of the core-shell nanocomposite with respect to that of Polyaniline due to the incorporation of ferrites. Raman spectroscopy confirmed TGA, DTA and XRD studies, and revealed that pure PAni is less stable than the corresponding core-shell nanocomposite with respect to molecular changes which might occur during heating at elevated temperatures. Moreover, Raman study confirmed the interfacial interaction between the core and the shell materials, and lead to an assumption about the presence of different conjugation chain lengths and types, such as the presence of the semi-quinones aside the quinone rings in the polymer chain, which showed different response upon heating the sample. (C) 2011 Elsevier B.V. All rights reserved.