Marcus Tegel

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The ternary iron arsenide BaFe2As2 becomes superconducting by hole doping, which was achieved by partial substitution of the barium site with potassium. We have discovered bulk superconductivity at T{c}=38 K in (Ba1-xKx)Fe2As2 with x approximately 0.4. The parent compound BaFe2As2 crystallizes in the tetragonal ThCr2Si2-type structure, which consists of(More)
The new quaternary iron arsenide-fluoride SrFeAsF with the tetragonal ZrCuSiAstype structure was synthesized and the crystal structure was determined by X-ray powder diffraction (P4/nmm, a = 399.30(1), c = 895.46(1) pm). SrFeAsF undergoes a structural and magnetic phase transition at 175 K, accompanied by strong anomalies in the specific heat, electrical(More)
High-resolution X-ray diffraction data, in conjunction with DFT(B3LYP) quantum calculations, have been used in a QTAIM analysis of the charge density in the trimethylenemethane (TMM) complex Fe(eta(4)-C[CH(2)](3))(CO)(3). The agreement between the theoretical and experimental topological properties is excellent. Only one bond path is observed between the(More)
Polycrystalline samples of underdoped (Ba1−xKx)Fe2As2 (x ≤ 0.4) were synthesized and studied by x-ray powder diffraction, magnetic susceptibility, specific heat and Fe-Mössbauer-spectroscopy. The structural phase transition from tetragonal to orthorhombic lattice symmetry shifts towards lower temperatures, becomes less pronounced at x = 0.1-0.2 and is no(More)
The structural and magnetic phase transitions of the ternary iron arsenides SrFe2As2 and EuFe2As2 were studied by temperature-dependent x-ray powder diffraction and Fe Mössbauer spectroscopy. Both compounds crystallize in the tetragonal ThCr2Si2-type structure at room temperature and exhibit displacive structural transitions at 203 K (SrFe2As2) or 190 K(More)
The discovery of high-Tc superconductivity in iron arsenides in 2008 has arguably been the biggest breakthrough in this field since the appearance of the copper oxide superconductors in 1986. In iron arsenides, superconductivity up to 55 K originates in layers of edge-sharing [FeAs4/4]-tetrahedra. Meanwhile, a series of different structure types have been(More)
New nitridosilicates Ca(3)Sm(3)[Si(9)N(17)] and Ca(3)Yb(3)[Si(9)N(17)] were synthesized from the reactions of the pure metals (calcium and samarium/ytterbium) with silicon diimide "Si(NH)(2) " in a radio-frequency (rf) furnace at temperatures of up to 1650 °C. These isotypic compounds crystallize in the cubic space group P4(-)3m (no. 215) with lattice(More)
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