Crystallographic and 119Sn and 155Gd Moessbauer analyses of Gd5Ge2(Si1-xSnx)2 (x = 0.23 and x = 0.40)

We report the structural characterization of Gd5Ge2(Si1-xSnx)2 (x = 0.23 and x = 0.40) compounds by means of 100 and 298 K-X-ray diffractometry (XRD) and 4 K-155Gd and 298 K-119Sn Moessbauer spectroscopy. These compounds order ferromagnetically at 218.4 and 172.7 K, respectively. At ∼100 K, it was identified the Gd5Si4-orthorhombic phase (type I) for both samples. At ∼298 K, it was identified a Gd5Si2Ge2-monoclinic phase, for x = 0.23 and a Sm5Sn4-orthorhombic phase (type II), for x 0.40. The Rietveld analysis of XRD data suggests a first order magneto-structural transition at Curie temperature for both compositions. Moessbauer results are well consistent with the proposed crystallographic models for these systems.