Air‐Stable Carbon‐Fe Based Magnetic Nanostructures

Herein, we report a simple solid state synthetic route to prepare carbon-Fe based magnetic nanoparticles with different compositions and morphologies through annealing of amorphous Fe nanoparticles under appropriate conditions. Tri-n-octylphosphine (TOP) capped amorphous Fe nanoparticles with a mean diameter of 3.2 nm were synthesized using solvated metal atom dispersion (SMAD) method. Annealing of as-prepared Fe nanoparticles at 300 °C produced carbon encapsulated crystalline bcc-Fe nanoparticles, whereas at higher temperatures i.e., 400 °C and 500 °C, spherical Fe 3 C/C core-shell nanoparticles were obtained. Annealing of as-prepared Fe nanoparticles in the presence of tri-n-octylphosphine oxide (TOPO) ligand under optimized conditions yielded rod shaped Fe 3 C/C core-shell morphology. The size, composition and particle morphology of these magnetic nanoparticles could be controlled by changing the reaction time, temperature and the concentration of the TOPO ligand. Magnetic measurements show that rod shaped Fe 3 C nanoparticles exhibit enhanced coercivity (Hc) values compared with spherical Fe 3 C nanoparticles, which is due to shape anisotropy. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim