Structure and properties of Eu2Pt3Sn5

The new stannide Eu2Pt3Sn5 was synthesized by induction melting of the elements in a sealed tantalum tube in a water-cooled silica sample chamber. The structure was refined on the basis of single crystal X-ray diffractometer data: Y2Rh3Sn5 type, Cmc21, a = 453.30(9), b = 2662.9(8), c = 731.8(2) pm, wR2 = 0.0472, 1493 F2 values and 62 variables. The platinum and tin atoms build up a complex three-dimensional [Pt3Sn5] network with a broad range of Pt-Sn (264-293 pm) and Sn-Sn (308-373 pm) distances. The two crystallographically independent europium sites occupy large voids of coordination numbers 20 (Eu1) and 18 (Eu2) within the [Pt3Sn5] network. Eu2Pt3Sn5 shows Curie-Weiss behaviour in the temperature range 50-305 K with an experimental magnetic moment of 7.82(1) μB per Eu atom indicating purely divalent europium. Cp measurements show a broad anomaly with two maxima at 4.9(2) and 6.1(2) K. 151Eu Moessbauer spectra revealed both crystallographically independent europium sites to be divalent. At 4.2 K two rather different sizes of magnetic hyperfine field splittings are observed due to separate ordering of the two sites. The 119Sn Moessbauer spectrum shows complex superposition of the five signals in the paramagnetic range. (orig.)