Structural and magnetic properties of carbon-encapsulated Fe/Fe3C nanoparticles

Carbon-encapsulated iron-cementite (Fe/Fe3C) magnetic nanoparticles were synthesized by an upscalable solid-state pyrolysis method using iron phthalocyanine as a precursor. The dependence of the structure, morphology and magnetic properties on the pyrolysis conditions is presented. The nanocomposite contains nanoparticles made of cementite with a small fraction of iron, with an average diameter of 15 nm embedded in an amorphous carbon matrix. A 3 nm thick graphite shell is formed on the surface of the particles. The volume fraction of α-Fe increases almost linearly on increasing pyrolysis temperature: from 0.5% for the sample synthesized at 800 ◦C up to 11% for a 900 ◦C pyrolysis temperature, resulting in an increase of the saturation magnetization from 14.0 to 17.74 Am2/kg and a decrease of the coercivity from 49.34 to 10.74 kA/m