Magnetic and magnetoresistance behaviors of solvent extracted particulate iron/polyacrylonitrile nanocomposites

Iron nanoparticle reinforced polyacrylonitrile (PAN) nanocomposites are fabricated by a facile and environmentally benign solvent extraction method. Fourier transform infrared (FT-IR), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC) results indicate a strong interaction between the iron nanoparticles and the polymer matrix for the as-prepared polymer nanocomposites. The heat treatment induces the carbonization of the polymer matrix. High-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) analysis show a protecting carbon shell surrounding the iron nanoparticles within the carbon matrix against the particle oxidation. The magnetic properties, electrical conductivity, and magnetic field dependent resistivity of heat-treated nanocomposites with different particle loadings are carried out in a physical properties measurement system by Quantum Design and by a standard four probe method. The saturation magnetization increases and the coercivity decreases with an increase of the nanoparticle loading. The heat-treated nanocomposites possess a room temperature magnetoresistance (MR) of 5.1% at a field of 90 kOe. The nanoparticle loading has a significant effect on the resistivity of nanocomposites. The heattreated nanocomposites show a particle loading dependent transport mechanism. A transition from semiconductive to metallic conduction was observed with an increase of the nanoparticle loading. © 2010 American Chemical Society