Low-Temperature Magnetic Properties of Nanometric Fe-Based Particles

Fe-based nanoparticles were prepared by laser-driven pyrolysis. The as-synthesised powder consists ofα-Fe and $Fe_3O_4//γ-Fe_2O_3$ nanoparticles embedded in a pyrolytic carbon matrix. The crystallite size of 1.8 nm forα-Fe was calculated using the Scherrer formula. The as-synthesised nanopowder was superparamagnetic. The maximum of the zero-field cooling curve was observed at 32 K and the distribution of blocking temperatures $g(T_B)$ peaked at 11 K. As a result of small particle sizes and the soft matrix, the Lamb-Mössbauer factor f was significantly higher at 4 K than at 293 K