A Mössbauer Spectral Study of Tb₂Fe₁₇ and the Tb₂Fe₁₇₋ₓSiₓ Solid Solutions

The Mössbauer spectra of a series of rhombohedral Tb2Fe17-xSix solid solutions, with x equal to 0, 1, 2, and 3, have been measured as a function of temperature. Although the spectra of Tb2Fe17 change substantially upon cooling from 295 to 85 K, it has been possible to fit them with a consistent seven sextet model corresponding to a basal magnetization. The spectral analysis yields reasonable hyperfine parameters and the expected changes with temperature. The resulting weighted average effective iron recoil mass of 66 g/mol and the Mössbauer temperature of 395 K are typical of this type of intermetallic compound. In addition, the isomer shifts and the hyperfine fields observed for the crystallographically distinct iron sites in Tb2Fe17 agree well with those expected from the differences in the Wigner-Seitz cell volumes and the near-neighbor environments of the four sites. The spectra of the silicon substituted solid solutions have been fit with the same model and similar hyperfine parameters, but with a binomial distribution of near-neighbor environments. The weighted average hyperfine field decreases slowly with increasing silicon content, whereas the isomer shift increases