Mossbauer effect studies of Nd2Fe14-xSix B and Y2Fe14-xSixB

The Mossbauer effect spectra of the solid solutions of Nd₂ Fe_14-xSi_xB, with x equal to 0.00, 0.25, 0.50, 0.75, 1.0, 1.5, and 2.0, and Y₂Fe_14-xSi_xBi, with x equal to 0.0, 1.0, 1.5, and 2.0, have been measured at 295 K. The results are most consistent with a random distribution of the silicon over the smaller 16k₁, 16k₂, 8j₁, 4c, and 4e iron sites in Nd₂Fe₁₄B. Apparently, the silicon is, at least in part, excluded from the 8j₂ site, which is the site with the largest Wigner-Seitz volume. The results do not, however, rule out other possible silicon site occupancy models. The isomer shift increases slightly with increasing silicon content, whereas the quadrupole interaction remains virtually constant. The hyperfine field decreases with increasing silicon content, but the apparent linewidth increases. These changes have been modeled in terms of a distribution of hyperfine fields on each site which is determined by a binomial distribution of silicon on the Wigner-Seitz near neighbors of each iron site