Morphology and magnetic properties of the iron oxide layer formed on iron acicular particles

Iron oxide layer was formed on iron acicular particles to protect the particles from further oxidation. The typical thickness of the oxide layer was about 30 A, and the saturation magnetization in the oxide layer was calculated to be about 40 emu/g at 300 K. It was found that the oxide layer consisted of ferromagnetic iron oxides and superparamagnetic region, and the ferromagnetic iron oxides acted as protection layer against further oxidation of particles.