Inelastic neutron scattering investigation of ball-milled FeSiB described as a magnetic nanoglass-like structure

An inelastic neutron scattering study has been carried out to assess the effects of mechanical milling treatments (10, 20 and 70 h) on an amorphous melt-spun FeSiB ribbon. Faint traces of crystallization were observed after 10 and 20 h milling by X-ray diffraction and Mössbauer spectroscopy and a minor fraction of bcc-Fe was clearly detected after 70 h. Whilst the neutron spectrum S(E) of the 10 h-milled sample, at temperature T = 300 K, does not differ from that of the precursor FeSiB ribbon, the area of the inelastic region of S(E) decreases more and more after 20 and 70 h milling. Moreover, in the samples milled for 20 and 70 h, also the area of the elastic region of the S(E) spectrum is definitely smaller than the one of the FeSiB ribbon. This is consistent with a reduction of the magnetic cross section upon milling and it agrees also with magnetization measurements. We interpret this behavior assuming that the milling treatment causes local alterations of the short-range atomic order within the amorphous phase, and hence of the precursor collinear ferromagnetic order, finally giving rise to a sort of magnetic nanoglass structure.