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.

Fe-B-Ag multilayers have been prepared in two different sequences of the layers in order to reveal distinctness of "top" and "bottom" interfaces of each element in relation to the other two elements. Transmission electron microscopy analysis showed a much larger interface roughness for the Fe/ B/Ag ͑i.e., Fe at bottom, Ag on top of B͒ than for the B/Fe/Ag sequence, which is mainly due to the different growth processes of Ag. For both sequence Fe and B layers of 2 nm thickness are continuous and solid state amorphization-similar to that observed in Fe/B multilayers-takes place during sample growth. Mössbauer spectroscopy measurements indicate that the amorphous interface has a broad bimodal concentration distribution for both layer sequence, but intermixing is larger at the Fe/B than at the B/Fe interface.

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After ball-milling nonmagnetic FeAl a grain structure resembling to a rigid magnetic foam is indicated by Mössbauer spectroscopy. It consists of nanosize nonmagnetic grains with ferromagnetic boundaries formed by about two atomic layers of Fe. The magnetic behavior is uncommon: (i) the transition to the paramagnetic state is glass-like and magnetic relaxation sets in at low temperatures; (ii) the magnitude of the local Fe magnetic moments decreases linearly with temperature; (iii) in high fields a strongly anisotropic ferromagnetic behavior is observed.

Equiatomic composition powder mixture of pure Fe and B was mechanically alloyed in a controlled atmosphere vibration mill. Amorphous alloy phase formation was established by Mijssbauer spectroscopy and by transmission electron microscopy. The variation of the average boron concentration and the homogeneity of the amorphous phase during the alloying process was followed by MSssbauer spectroscopy. At the early stage of the milling process a broad concentration distribution (from 20 to 50 at. % Bj was observed. Upon further milling the average B concentration of the amorphous component was gradually enhanced and the concentration heterogeneity decreased. The B concentration of the amorphous phase could be further enhanced by heat treating the milled powder mixture. The highest boron Fe,,B,. 0 199.