Structure, magnetic properties and151Eu, 119Sn mössbauer spectroscopy of Eu5Sn3S12 and Eu4LuSn3S12

Eu5Sn3S12 and Eu4LuSn 3S12 were synthesized and their structures refined from single crystal data (Pmc21; Eu5Sn3S 12: a = 3.908(1), b = 20.115(4), c = 11.451(2) Å; wR2 = 0.0519 for 3048 F2 and 122 parameters; Eu4LuSn3S 12: a = 3.920(1), b = 20.132(4), c = 11.459(2) Å; wR2 = 0.0737 for 3298 F2 and 122 parameters). The structures contain one-dimensional chains of edge-sharing SnS2S4/2 octahedra and corner-sharing SnS3S2/2 trigonal bipyramids, running parallel to [100]. Five europium sites are seven- or eightfold coordinated by sulfur atoms. Lutetium atoms in Eu4LuSn3S12 show a strong site preference for one of the two Eu3+ positions of Eu5Sn3S12 and no structural disorder was observed. Both compounds show static mixed valence according to Eu 32+Eu23+Sn34+S122- and Eu32+Eu 3+Lu3+Sn34+S122-, which was confirmed by temperature dependent magnetic susceptibility measurements. The experimental magnetic moments of 14.6(1) (Eu5Sn3S12) and 14.1(1) (Eu 4LuSn3S12) μB/f.u. indicate that each of the two sulfides contains three divalent europium atoms per formula unit. Magnetic ordering for Eu5Sn3S12 and Eu4LuSn3S12 sets in below 5 and 3 K, respectively. Both sulfides show metamagnetic or spin-flip transitions in the magnetization curves at 3 K (2 K) with full saturation of the europium magnetic moments at 3 K (2 K) and 80 kOe. 151Eu Mössbauer spectra fully confirm the Eu2+ and Eu3+ site occupancies. At 4.2 K an increase in line width indicates small hyperfine fields at the europium nuclei. © 2007 Verlag der Zeitschrift für Naturforschung.