Mossbauer study of the interface of iron nanocrystallites

The hyperfine parameters of iron atoms are studied in iron nanocrystallites prepared by different methods: ball milling of iron powder, partial crysta llization of Fe-Zr-B-Cu amorphous ribbons, and vacuum evaporation of Fe-B p olycrystalline multilayers. Careful analysis of the spectral contribution o f the possible impurities and chemical mixing at interfaces reveals that no specific grain boundary contribution can be separated in the Mossbauer spe ctra when the grain size is in the 2-10 nm range. The results indicate that excluding chemical effects the hyperfine fields of iron atoms at the bce i nterfaces are very close to those in the bulk, and Mossbauer spectra of the iron nanocrystallites studied can be understood without supposing a separa te grain boundary phase with very distorted structure or highly reduced den sity.