The effect of oxidized surface layers on the inner core of fine iron particles

Abstract

Mössbauer measurements on fine iron particles with the size ranging from 150 to 350 Å with oxidized surface layer are carried out between 81 and 300K. The spectra consist of two components, a component due to metallic iron and a second component with a larger hyperfine field. The thickness of the oxide surface layer calculated from the area ratio of the subspectra is about 19 Å, and is independent of the average diameter of the particles. A slight enhancement of the hyperfine field of the iron core with a decrease of particle size has been observed. It results from the contribution of the atoms at the interface layer and the dipole interaction between the particles. The dipole interaction decreases owing to the effects of the oxide surface layer on the dipole field.