Synthesis of ferromagnetic nanoparticles with a core/shell structure by a self-propagating combustion method

Ferromagnetic nanoparticles with a core/shell structure were fabricated by a self-propagating combustion method and subsequent hydrogen reduction process. Before the reduction process, synthesized particles were Fe oxide phases. Transmission electron micrographs confirmed that the nanoparticles were composed of α-Fe core and Fe–Al oxide shell after the reduction process. The saturation magnetization of the nanoparticles was measured about 180 emu/g and the permeability kept constant value of about 1.8 up to 10 GHz without any noticeable loss. These microstructural and magnetic analyses showed that the oxide phase changed into α-Fe and then Al atoms diffused out to the surface of the particles during the reduction process.