Tin‐rich Phases RE2Au3Sn6 with RE = La, Ce, Pr, Nd, Sm – Synthesis, Structure, Magnetic Properties, and 119Sn Mössbauer Spectra

Abstract

The stannides RE2Au3Sn6 (RE = La, Ce, Pr, Nd, Sm) were synthesized from the elements by arc‐melting. Small single crystals were grown by annealing samples in sealed tantalum tubes in an induction furnace with a special annealing sequence. The polycrystalline phases were characterized through their X‐ray powder diffraction pattern. The structures of Ce2Au3Sn6, Pr2Au3Sn6, and Nd2Au3Sn6 were refined from single‐crystal X‐ray diffractometer data. The RE2Au3Sn6 stannides crystallize with the orthorhombic La2Zn3Ge6 type, space group Cmcm. The basic structural building units are Au1@Sn4 tetrahedra and Au2@Sn5 square pyramids. These units are condensed to layers and the structure can be described by a simple stacking of tetrahedral and pyramidal layers with the rare earth cations in between. Temperature dependent susceptibility studies indicate that all rare earth atoms are in the trivalent oxidation state, as their effective magnetic moments match the expected values of the free RE3+ ions. Pr2Au3Sn6 and Nd2Au3Sn6 exhibit antiferromagnetic ordering at TN = 6.3(1) and 6.7(1) K. Investigations of the electrical resistivity of La2Au3Sn6 and Ce2Au3Sn6 confirmed that these compounds are metallic, for La2Au3Sn6 a lower resistivity was observed, in line with the absence of screening unpaired electrons. 119Sn Mössbauer spectra for La2Au3Sn6, Ce2Au3Sn6, Pr2Au3Sn6 and Nd2Au3Sn6 show a complex superposition of three sub‐spectra which can be differentiated through their distinctly different quadrupole splitting parameters. The isomer shifts (1.87 to 2.22 mm·s–1) indicate significant s electron density at the tin nuclei.