Mössbauer study of some 2-17 lanthanide-iron compounds

We have studied the iron-rich, rare-earth-iron intermetallic compounds R₂Fe₁₇ (R = Pr, Gd, Tm, Lu), using the Mössbauer effect in ⁵⁷Fe. The measured average hyperfine field H(T/T _c) acting on the ⁵⁷Fe nuclei is a unique, monotonically decreasing function of T/T_c, with no observed irregularity at temperatures corresponding to a suspected ferromagnetic-antiferromagnetic phase transition in these compounds. The onset of paramagnetism occurs at temperatures close to the upper transition points measured by Strnat et al., namely at T_c = 282°, 472°, 271°, and 263°K for Pr ₂Fe₁₇, Gd₂Fe₁₇, Tm ₂Fe₁₇, and Lu₂Fe₁₇, respectively. Low-temperature (≃90°K) spectra indicate the presence of at least four magnetically nonequivalent Fe sublattices, while for T>T_c broadened 2-line absorption spectra typical of ⁵⁷Fe at noncubic sites in paramagnetic material are observed.