A Mossbauer spectral study of Tb2Fe17 and the Tb2Fe17-xSix solid solutions

The Mossbauer spectra of a series of rhombohedral Tb2Fe17-xSix solid soluti ons, with x equal to 0, 1, 2, and 3, have been measured as a function of te mperature. Although the spectra of Tb2Fe17 change substantially upon coolin g from 295 to 85 K, it has been possible to fit them with a consistent seve n sextet model corresponding to a basal magnetization. The spectral analysi s yields reasonable hyperfine parameters and the expected changes with temp erature. The resulting weighted average effective iron recoil mass of 66 g/ mol and the Mossbauer temperature of 395 K are typical of this type of inte rmetallic 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 vol umes and the near-neighbor environments of the four sites. The spectra of t he silicon substituted solid solutions have been fit with the same model an d similar hyperfine parameters, but with a binomial distribution of near-ne ighbor environments. The weighted average hyperfine field decreases slowly with increasing silicon content, whereas the isomer shift increases. (C) 19 98 American Institute of Physics. [S0021-8979(98)35611-X].