Superconductivity and magnetism in MPt4Ge12, M = Ca, Ba, Sr, Eu

Abstract

X-ray powder data for Ba0.8Ca0.2Pt4Ge 12 and X-ray single crystal data for EuPt4Ge12 define cubic body-centered symmetry consistent with novel Ge-based skutterudites SrPt4Ge12 and BaPt4Ge12 (space group Im3). Structural and electron microprobe analysis investigations evidence a complete filling of the icosahedral cages without large atomic displacement parameters. Ba0.8Ca0.2Pt4Ge12 exhibits phonon-mediated superconductivity at Tc = 5.2 K. Density functional theory (DFT) calculations (LDA+U) carried out for EuPt 4Ge12 proved that Eu guest atoms strongly stabilize the compound in which the calculated density of states around the Fermi energy essentially consists of hybridized Ge 4p-like and Pt 5d-like states. Low temperature resistivity studies evidence magnetic ordering at Tm ≈ 1.7 K. Susceptibility measurements reveal a divalent state for europium, in excellent agreement with the DFT calculations. ©2008 The Physical Society of Japan.