Mössbauer study of the oxides layer formed on the surface of acicular iron particles

The structure of the iron oxides layer formed on the surface of acicular iron particles is investigated by means of Mössbauer absorption measurements using a sample of which surface is made of enriched⁵⁷Fe. The iron oxides layer consists of ferrimagnetic Fe3O4and superparamagnetic Fe3O4at 300 K. The superparamagnetic region of Fe3O4diminishes below about 110 K. The volume ratio of the ferrimagnetic region to the superparamagnetic region of Fe3O4is calculated to be about 7:3 at 300 K.