Understanding the Stabilization and Tunability of Divalent Europium 2.2.2B Cryptates

Abstract The ternary platinides CaGa5Pt3 (a = 2082.5(4), b = 406.05(8), c = 739.2(1) pm) and EuGa5Pt3 (a = 2085.5(5), b = 412.75(9), c = 738.7(1) pm) were synthesized from the elements in sealed high-melting metal tubes in an induction furnace. CaGa5Pt3 and EuGa5Pt3 are isotypic with CeAl5Pt3 and isopointal with the YNi5Si3 type intermetallic phases (space group Pnma, oP36 and Wyckoff sequence c 9). The structure of EuGa5Pt3 was refined from single crystal X-ray diffractometer data: wR2 = 0.0443, 1063 F 2 values and 56 variables. The gallium and platinum atoms build up a three-dimensional [Ga5Pt3]2− polyanionic network in which the europium atoms fill slightly distorted hexagonal prismatic voids. The Ga–Pt distances within the network range from 249 to 271 pm, emphasizing the covalent bonding character. Temperature dependent magnetic susceptibility measurements indicate diamagnetism for CaGa5Pt3 and isotypic BaGa5Pt3. EuGa5Pt3 behaves like a Curie–Weiss paramagnet above 50 K with an experimental magnetic moment of 8.17(1) µB/Eu atom, indicating divalent europium. Antiferromagnetic ordering sets in at T N = 8.5(1) K. The divalent ground state of europium is confirmed by 151Eu Mössbauer spectroscopy. EuGa5Pt3 shows a single signal at 78 K with an isomer shift of −9.89(4) mm s−1. Full magnetic hyperfine splitting with a hyperfine field of 25.0(2) T is observed at 6 K in the magnetically ordered regime.

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Nickel-deficient Stannides Eu2Ni2–xSn5 – Structure, Magnetic Properties, and Mössbauer Spectroscopic Characterization

Zeitschrift für Naturforschung B ◽

10.1515/znb-2009-1003 ◽

2009 ◽

Vol 64 (10) ◽

pp. 1107-1114 ◽

Cited By ~ 3

Author(s):

Thomas Harmening ◽

Matthias Eul ◽

Rainer Pöttgen

Keyword(s):

Solid Solution ◽

Magnetic Properties ◽

Powder Diffraction ◽

Spectroscopic Characterization ◽

Structure Type ◽

Induction Melting ◽

X Ray ◽

Antiferromagnetic Ordering ◽

Divalent Europium ◽

Experimental Magnetic Moment

New nickel-deficient stannides Eu2Ni2−xSn5 were synthesized by induction melting of the elements in sealed tantalum tubes. The solid solution was studied by X-ray powder diffraction and two crystal structures were refined on the basis of X-ray diffractometer data: Cmcm, a = 466.03(4), b = 3843.1(8), c = 462.92(9) pm, wR2 = 0.0469, 692 F2 values, 39 variables for Eu2Ni1.49(1)Sn5 and a = 466.11(9), b = 3820.1(8), c = 462.51(9) pm, wR2 = 0.0358, 695 F2 values, 39 variables for Eu2Ni1.35(1)Sn5. This new structure type can be considered as an intergrowth structure of CaBe2Ge2- and CrB-related slabs. The striking structural motifs are nickel-centered square pyramids which are condensed via common corners and edges. The layers of condensed NiSn5 units are separated by the europium atoms. The Ni1 sites within the CaBe2Ge2 slabs show significant defects which leads to split positions for one tin site. Eu2Ni1.50Sn5 shows Curie-Weiss behavior and an experimental magnetic moment of 7.74(1) μB / Eu atom, indicating stable divalent europium, as is also evident from 151Eu Mössbauer spectra. Antiferromagnetic ordering is detected at 3.5 K.

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