Magnetic properties of nanometric Fe-based particles obtained by laser-driven pyrolysis

Fe-based nanoparticles were prepared by laser pyrolysis method using a cross-flow reactor in which the CO2 laser radiation orthogonally crosses with the stream of Fe(CO)5, C2H2, and C2H4 gases. The as-synthesised powder was characterised by HRTEM, XRD, Mössbauer spectroscopy, and low- and high-temperature magnetic measurements. The as-synthesised powder consisted of α-Fe and Fe3O4/γ-Fe2O3 nanoparticles embedded in a pyrolytic carbon matrix. The XRD pattern of the sample exhibited broad peaks. The crystallite size dXRD was estimated using the Scherrer formula and it was 1.8 nm for α-Fe and 1.6 nm for pyrolytic carbon. The as-synthesised nanopowder was superparamagnetic. The blocking temperature was determined from the maximum of the ZFC curve and it was 32 K. After the sample had been cooled down to 4 K, the Mössbauer-Lamb factor f strongly increased.