The RMgSn2 Series of Compounds (R = Rare Earth Metal): Synthesis, Crystal Structure, and Magnetic Measurements

The novel isostructural series of phases RMgSn2 (R = Y, La–Nd, Sm, Gd–Tm, Lu) is presented. They were prepared by direct synthesis in an induction furnace and subsequently annealed at 500 °C. Their crystal structures were determined through single-crystal X-ray diffraction analysis of the Ce representative [I42m, tI32-LaMgSn2, Z = 8, a = 0.82863(3) nm, c = 1.23129(5) nm] and confirmed by powder X-ray diffraction analysis of the other members of the series. Rietveld refinements were also performed on the homologues with R = Pr, Tm, and Y. The title phases show a unique space distribution of atoms, characterized by the presence of a Sn–Sn dumbbell distanced at around 0.29 nm. Their structures are related to those of a few binary AeTt3 (Ae = alkaline earth; Tt = Si, Ge; I4/mmm, tI32-YbSi3) compounds that are stable at high pressure, characterized by a more complex 3D covalently bonded Tt network. Compounds CeMgSn2 and TbMgSn2 were magnetically characterized; they show paramagnetic behavior with the presence of ferromagnetic interactions, more pronounced in the case of TbMgSn2, as suggested by the Curie–Weiss temperatures, determined in the high-temperature range, of 0.96 and 27.6 K for CeMgSn2 and TbMgSn2, respectively.