The Effect of Interlayer Cations on the Magnetic Properties of the Mixed-Metal Pnictide Oxides: A2MnZn2As2O2 (A = Sr, Ba)

The new pnictide oxide Sr2MnZn2As2O2 is reported. The crystal structure of this compound consists of a 1:1 intergrowth of square-planar MnO2 2- layers and ThCr2Si2-type Zn2As2 2- layers interspersed by Sr cations. This compound has been prepared by sintering the stoichiometric ratio of SrO, Mn, Zn, and As in a fused-silica ampule under 0.2 atm of Ar at 1000 °C for 1 week. The sample quality has been examined by Rietveld refinement of the powder X-ray diffraction data, and the transition metal site (2a and 4d) selectivity has been analyzed by Rietveld refinement of powder neutron diffraction data. Furthermore, effects of this structural order on the magnetic susceptibility and interaction between the magnetic layers have been analyzed by temperature-dependent magnetization measurements. The magnetic structures of both phases, A2MnZn2As2O2 (A = Sr, Ba), have been investigated by temperature-dependent powder neutron diffraction. The Ba analogue exhibits two-dimensional short-range order below about 40 K, whereas for the Sr analogue, no evidence for either long- or short-range order was found over the 2θ range investigated down to 4 K. The results of these characterizations are compared with those of the previously studied phase, Sr2Mn3As2O2.