Formation of stable magnetic nanoparticles by pyrolysis of metal containing polymers

Inorganic matrix magnetic nanocomposite, containing Fe3C nanocrystallites, was processed by an innovative fabrication method using frontal polymerisation of iron acrylamid complex (FeAAm), followed by further pyrolysis at 873 K/150 min. The pyrolysis product was in a form of porous, irregular powder particles having broad range of size distribution, from 50 up to 500 mu m. The powder particles contain nanocrystallites of Fe3C having mean size 10-80 nm. The plot of magnetisation versus external magnetic field is characteristic of ferromagnetic material with well-defined hysteresis loops. Saturation magnetisation is 40 emu/g and slightly depends on the temperature. Substantial temperature dependence exhibits the coercivity, which decreases from 0.27T for 4K down to 0.06T for 300 K. The material does not exhibit superparamagnetic behaviour. (c) 2007 Elsevier B.V. All rights reserved.