The hyperfine parameters of iron atoms are studied in iron nanocrystallites prepared by different methods: ball milling of iron powder, partial crystallization of Fe-Zr-B-Cu amorphous ribbons, and vacuum evaporation of Fe-B polycrystalline multilayers. Careful analysis of the spectral contribution of the possible impurities and chemical mixing at interfaces reveals that no specific grain boundary contribution can be separated in the Mössbauer spectra 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 bcc interfaces are very close to those in the bulk, and Mössbauer spectra of the iron nanocrystallites studied can be understood without supposing a separate grain boundary phase with very distorted structure or highly reduced density.

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The magnetic behaviour of nanosize ferromagnetic bcc granules embedded in an amorphous tissue (i.e., partially crystallized Fe 80 Zr 7 B 12 Cu amorphous alloy) was studied by 57 Fe Mössbauer spectroscopy. The results are compared with the bulk counterparts: bcc-Fe and amorphous Fe 2 B 0.625 Zr 0.375. Size dependent enhancement of the Curie point of the nanosize amorphous phase was not observed. At temperatures well above the Curie point of the amorphous phase superparamagnetic relaxation of the bcc crystallites is observed opening new possibilities to study the anisotropy energy of nanosize ferromagnetic grains.