A Mossbauer spectral study of some magnetic rear-earth iron intermetallic compounds

In this thesis the Mössbauer spectra of Ce₂Fe₁₇ H_x, where x is 0, 1, 2, 3, 4, and 5, Pr ₂Fe₁₇H_x, where x is 0, 1, 2, 3, 4, and 5, Dy₂Fe₁₇H_x, where x is 0, 1, 2, 3, and 3.8, Tb₂Fe_17-xSi_x, where x is 0, 1, 2, and 3, and Nd₆Fe₁₃X, where X is Au, Ag, Cu, and Si, have been measured between 450 to 4.2 K.; Ce₂Fe₁₇ crystallizes in the R-3m space group and exhibits a helical magnetization from 225 to 90 K and a fan magnetization below 90 K. The helical magnetization was modeled in the Mössbauer spectra by a distribution of &thetas; angles and hyperfine fields. The hyperfine parameters were found to have the expected temperature dependence and to be in good agreement with the hyperfine parameters found for the hydrides. Pr ₂Fe₁₇H₅ is the first R₂ Fe₁₇H_x compound to show an unusual change in the Mössbauer spectra below 155 K, a change which was attributed to the freezing of the motion of the 18g hydrogen from site to site on the Mössbauer time scale. Dy₂Fe₁₇H_x crystallizes in the hexagonal P6₃/mcm space group and exhibits a disorder of the 4e, 4f iron and 2c, 2d dysprosium site, a disorder which was modeled in the observed Mössbauer spectra.; Tb₂Fe_17-xSi_x, shows an unexpected improvement in the magnetic properties with increasing silicon content in spite of a contration of the unit cell upon the substitution of iron by silicon.; Nd₆Fe₁₃X crystallizes in the I4/ mmc space group and exhibits a basal magnetization for X = Ag, Au, and Cu. Nd₆Fe₁₃Si shows a spin reorientation from axial at 155 K towards basal at 80 K.