High coercivity below percolation threshold in polymer nanocomposite

The magnetic properties of nanocomposites of polymer and magnetic (carbon cased iron carbide) nanoparticles have been studied from 300 to 10 K. The nanocomposites show an enhanced coercivity and they retain the magnetic properties at very low concentration of filler. The high coercivity is produced due to dipolar interaction between nanoparticles. A low value of Mr/Ms is observed for nanocomposites, which increases at low temperatures. The dependence of saturation magnetization on temperature follows Bloch's T3/2 law and a departure from that is observed at higher temperatures. The Mössabauer spectra of nanocomposites show a sextet, which correspond to a ferromagnetic behavior of nanocomposites