Rainer Niewa

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The iron nitridometalates Li2[(Li(1-x)Fe(I)(x))N] display ferromagnetic ordering and spin freezing. Large magnetic moments up to 5.0mu(B)/Fe are found in the magnetization. In Mössbauer effect studies huge hyperfine magnetic fields up to 696 kOe are observed at specific Fe sites. These extraordinary fields and moments originate in an unusual ligand field(More)
Our attempts to synthesize the hitherto unknown binary copper(I) fluoride have led to first successes and a serendipitious result: By conproportionation of elemental copper and copper(II) fluoride in anhydrous liquid ammonia, two copper(I) fluorides were obtained as simple NH3 complexes. One of them presents an example of ligand-unsupported "cuprophilic"(More)
CeiMnNj was prepared by reaction of cerium nitride and manganese with nitrogen gas at 900 °C. It crystallizes isotypic to AC2MN3 (Ac = U, Th; M = Cr, Mn) and Ce^CrN^, space group Immm (No. 71), a = 3.74994(6) A, b = 3.44450(6) A and c = 12.4601(2) A. The manganese atoms are coordinated in a nearly square planar fashion by four nitrogen atoms. These(More)
Single crystals of ZnF2(NH3)3 and ZnF2(NH3)2 were obtained under ammonothermal conditions (250 °C, 196 MPa and 500 °C, 136 MPa). Upon thermal decomposition of both ZnF2(NH3)3 and ZnF2(NH3)2, a microcrystalline powder of ZnF2(NH3) was obtained. ZnF2(NH3)3 and ZnF2(NH3)2 represent probable intermediates in a conceivable ammonothermal synthesis of the(More)
field (B) independent −jAjT1=2 term in the temperature (T) evolution of the resistivity (ρ) in ZrAs1.58Se0.39 is compatible with the Altshuler-Aronov correction due to the electron-electron interaction (EEI) in weakly disordered metals [1]. The argument is based on the presence of a potentially strong lattice anisotropy in ZrAs1.58Se0.39, allegedly(More)
A representative of the fluoride-containing iron pnictide high-temperature superconductors, namely CaFFeAs, was doped with sodium up to the composition Ca0.86Na0.14FFeAs for the first time. Single crystals with an edge length in the range of 0.1 - 2.0 mm were obtained via solid-state and flux syntheses, respectively. The composition of the crystals was(More)
Lattice parameters a/pm 387.57(9) 387.57(2) 387.65(2) 387.68(3) c/pm 858.4(2) 859.48(5) 859.89(6) 859.87(9) c/a 2.215 2.218 2.218 2.218 Formula units per unit cell Z 2 Molar volume Vm/cm ∙mol 38.83 38.87 38.91 38.91 Calculated density Dx/g∙cm −3 4.89 4.87 4.84 4.82 Diffractometer Nonius KappaCCD (Bruker AXS, Karlsruhe, Germany) Radiation Mo-Kα (λ = 71.07(More)
Li(3)[ScN(2)] was prepared from Li(3)N with Sc or ScN in a nitrogen atmosphere at 1020 K as a light yellow powder with an optical band gap of about 2.9 eV. The crystal structure was refined based on X-ray and neutron powder diffraction data (Ia$\bar 3$, Z=16, X-ray diffraction: R(profile)=0.078, R(Bragg)=0.070; Neutron diffraction: R(profile)=0.077,(More)
The coexistence of three valence states of Mn ions, namely, +2, +3, and +4, in substituted magnetoplumbite-type BaFe12-xMnxO19 was observed by soft X-ray absorption spectroscopy at the Mn-L2,3 edge. We infer that the occurrence of multiple valence states of Mn situated in the pristine purely iron(III) compound BaFe12O19 is made possible by the fact that the(More)