A Magnetic and Mössbauer Spectral Study of SmFe₁₁Ti, LuFe₁₁Ti, and Their Respective Hydrides

ac Magnetic susceptibility measurements have been carried out on LuFe ₁₁ Ti and LuFe ₁₁ TiH and reveal the absence of any spin-reorientation between 4.5 and 293 K. Iron-57 Mössbauer spectral measurements between 4.2 and 295 K have been carried out on SmFe ₁₁ Ti and LuFe ₁₁ Ti and their respective hydrides, SmFe ₁₁ TiH and LuFe ₁₁ TiH. The Mössbauer spectra have been analyzed with a model that considers both the orientation of the iron magnetic moments and the distribution of titanium atoms in the near neighbor environment of the three crystallographically distinct iron sites. The assignment and the temperature dependence of the hyperfine fields are in complete agreement with the unit cell volume and its expansion upon hydrogenation and with those observed in the related RFe ₁₁ Ti and RFe ₁₁ TiH compounds. The site assignments and their temperature dependencies of the isomer shifts are in complete agreement both with the Wigner-Seitz cell volumes of the inequivalent iron sites and the crystallographic changes upon hydrogen insertion.