After a first meeting in Lima in 1996, our group (Non-Crystalline Solids) at the University of Sevilla begun a fruitful scientific collaboration with Jean Marc Greneche. Fe-57 Mössbauer spectroscopy (MS) has been an especially useful tool for studying Fe and Co-based nanocrystalline and multicomponent amorphous alloys, where a variety of environments exists for each atomic species, due to its character of sensitive local probe. Also, MS provides an invaluable complement of X-ray diffraction and magnetic measurements. In this work we will review the main results derived of our collaboration. We proposed a method to describe accurately Mössbauer spectra recorded on nanocrystalline FINEMET-type alloys by means of two independent components that were associated to different local environments. The refinement of Mössbauer spectra allowed to compare the kinetics and the local structural rearrangement mechanisms associated with the nanocrystallization process. Also, the combined use of x-ray diffraction and Mössbauer spectrometry allowed to estimate the compositions of both the nanocrystalline grains (Fe,Co,Mn)(Si, Al) and the amorphous residual phase of FINEMET and HITPERM nanocrystalline alloys with several compositions, allowing to establish how the different species partition to the amorphous matrix. These results were corroborated by results from different complementary techniques including x-ray diffraction, electron microscopy and atom probe.  We have also presented a comparative study of the effects of partial substitution of Co for Fe on thermal stability, crystallization and magnetic properties of Co-containing FINEMET and HITPERM alloys series. The difference in metalloid and Nb content between the two alloy series and the presence of Si in the nanocrystals in the case of FINEMET alloys appeared as key parameters with clear effect in Móssbauer spectra. Later on, Mössbauer spectroscopy allowed to characterize the hyperfine structure of the amorphous phase in FeCoSiAlGaPCB multicomponent alloys with different compositions and, also, of the nanocrystalline phase emerging in Cu-containing (Fe, Cr, Mo) (Ga, P, C, B) alloys.  The active cooperation, the opportunity to develop short stays at Jean Marc’s lab and his guidance allowed the development of a productive Mössbauer spectroscopy research line in our group at the University of Sevilla.

Mössbauer studies of Fe and Co-based nanocrystalline and multicomponent amorphous alloys

ACS Fall 2021

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