Synthesis and Characterization of a New Compound with Alternating MnO22- and Zn2As22- Layers: Ba2MnZn2As2O2

A new mixed transition metal pnictide oxide, Ba2MnZn2As2O2, is reported. Ba2MnZn2As2O2 has been prepared in quantitative yield from heating stoichiometric amounts of BaO with the elements, which are pressed into a pellet, placed in an Al2O3 boat, and sealed in a fused silica ampule, at 1000 °C. This compound is an ordered variant of the Sr2Mn3As2O2 structure type and crystallizes in the tetragonal space group I4/mmm (Z = 2). Single-crystal X-ray data (130 K) were refined (a = 4.2317(3) A, c = 19.443(2) A, R1 = 2.96%, wR2 = 6.84%). The structure is made up from square planar MnO2 layers with layers of Zn2As2 tetrahedra interspersed by alkaline earth cations such that the formula may be written as Ba2(MnO2)(Zn2As2). Rietveld refinement (a = 4.24257(8) A, c = 19.5087(7) A, Rwp = 9.26%, Rp = 6.44%) of powder neutron diffraction data obtained at room temperature provides unambiguous evidence for this ordered model in the case of Ba2MnZn2As2O2. Magnetic studies in the temperature range 5 ≤ T/K ≤ 300 show antife...