Fe1xNix samples with 0:225pxp0:400 were prepared by mechanical alloying. XRD studies showed that this group of samples
presents the bcc and fcc phases in all the composition ranges. The variation of the lattice parameter, a, of the two phases as a function of
the Ni content, remains independent of the composition. In this case all Mo¨ ssbauer spectra were fitted using a hyperfine field distribution
(HFD). Samples between 22.5 and 32.5 at% Ni present a paramagnetic site. For sample with 25 at% Ni, it was used an additional sextet
to obtain a good fit. From the Mo¨ ssbauer fitting in the field distributions, besides the field associated to the bcc and fcc microcrystalline
phases (between 30 and 33 T), additional peaks at smaller fields can be noticed (between 10 and 27 T). These small fields can be associated
with the contribution of those Fe magnetic sites localized in the surface and interfaces of the grains. This contribution is postulated as a
consequence of the nanometer size of the bcc and fcc grains obtained by DRX. |
