Chemical bonding in EuTGe (T=Ni, Pd, Pt) and physical properties of EuPdGe

EuPdGe was prepared from the elements by reaction in a sealed tantalum tube in a high-frequency furnace. Magnetic susceptibility measurements show Curie–Weiss behavior above 60 K with an experimental magnetic moment of 8.0(1)μB/Eu indicating divalent europium. At low external fields antiferromagnetic ordering is observed at TN=8.5(5) K. Magnetization measurements indicate a metamagnetic transition at a critical field of 1.5(2) T and a saturation magnetization of 6.4(1)μB/Eu at 5 K and 5.5 T. EuPdGe is a metallic conductor with a room-temperature value of 5000±500 μΩ cm for the specific resistivity. 151Eu Mössbauer spectroscopic experiments show a single europium site with an isomer shift of δ=−9.7(1) mm/s at 78 K. At 4.2 K full magnetic hyperfine field splitting with a hyperfine field of B=20.7(5) T is observed. Density functional calculations show the similarity of the electronic structures of EuPdGe and EuPtGe. T–Ge interactions (T=Pd, Pt) exist in both compounds. An ionic formula splitting Eu2+T0Ge2− seems more appropriate than Eu2+T2+Ge4− accounting for the bonding in both compounds. Geometry optimizations of EuTGe (T=Ni, Pt, Pd) show weak energy differences between the two structural types.

Cutouts of the [PdGe] and [PtGe] polyanions in the structures of EuPdGe and EuPtGe. Atom designations and some relevant interatomic distances are given.Figure optionsDownload as PowerPoint slide