Mossbauer-Spectroscopy Characterization of Nanostructured Magnetic Materials

Abstract

Two mechanisms are examined underlying the formation of the magnetic hyperfine structure in the Mössbauer spectra of magnetic materials containing nanoparticles. The absorption spectra of 57 Fe nuclei in FeCu-Nb-B nanostructured magnetic alloys are evaluated within the generalized two-level relaxation model, which includes interparticle interaction. All the unconventional features of the spectra are thus explained in qualitative terms. Furthermore, the precession of the magnetic moments of nanoparticles in a magnetic anisotropy field is investigated. It is shown that in a precessing hyperfine field the nuclear g factors should be subject to renormalization. As a result, the hyperfine spectra should undergo a radical transformation. It is concluded that the conventional techniques of Mössbauer-spectra evaluation in the context of nanostructured magnetic materials should be modified to include the transformation. NANOSTRUCTURE CHARACTERIZATION