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

Abstract

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) μ B/Eu indicating divalent europium. At low external fields antiferromagnetic ordering is observed at T N=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) μ B/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 Eu 2+ T 0Ge 2− seems more appropriate than Eu 2+ T 2+Ge 4− accounting for the bonding in both compounds. Geometry optimizations of Eu TGe ( T=Ni, Pt, Pd) show weak energy differences between the two structural types.