Mechanical alloying (MA) of Fe1-xCrx powder mixtures was performed over a wide range of concentration. Both x-ray diffraction and TEM analyses show that, after 30 hours of milling, the powder particles consist of nanocrystalline grains less than 10 nm in size. The kinetics of mixing is studied by Mössbauer spectrometry. This is the first time that the FeCr mixing state has been studied as a function of the milling conditions and the initial powder composition. This mixing state is defined by a parameter (d) calculated from the hyperfine field values. The alloying process is weakly composition dependent (for x40 at.% Cr), but is linked to the energy input to the powder. Especially an energy threshold must be transferred to the powder to reach a complete alloying. By studying the hyperfine field distributions of the Mössbauer spectra (for Cr<40 at.%), it seems that the Fe1-xCrx nanograin cores are quite homogeneous in composition and have hyperfine parameters close to those of the bulk alloys.

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Sputtered Fe/Tb multilayers of various Fe and Tb thicknesses ͑0.22рt Fe р3.3 nm, 0.2рt Tb р1.9 nm͒ have been investigated by x-ray diffraction, Mössbauer spectrometry, and magnetic measurements in the 4.2-300 K temperature range. A compositionally modulated structure is shown with the appearance of pure amorphous iron in the center of the Fe layers thicker than 1.2 nm. When the Fe layers are thick enough ͑у2.2-2.4 nm͒, the Fe layers will crystallize. The magnetic properties ͑M ,T comp ,T c ,...͒ were analyzed in relation with Fe and Tb thicknesses and also with mean Tb composition. In agreement with the structure, the departure of magnetic properties from those of the corresponding amorphous alloys is observed when pure amorphous iron appears in the center of the layers. The dependence of the magnetic anisotropy axis on temperature and thicknesses is interpreted taking into account the composition modulation in the multilayers and the dominant magnetic subnetwork.