The effect of interlayer cations on the magnetic properties of the mixed-metal pnictide oxides: A(2)MnZn(2)As(2)O(2) (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 MnO22- layers and ThCr2Si2-type Zn2As22-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 degreesC for 1 wee k. The sample quality has been examined by Rietveld refinement of the powde r X-ray diffraction data, and the transition metal site (2a and 4d) selecti vity has been analyzed by Rietveld refinement of powder neutron diffraction data. Furthermore, effects of this structural order on the magnetic suscep tibility and interaction between the magnetic layers have been analyzed by temperature-dependent magnetization measurements. The magnetic structures o f both phases, A(2)MnZn(2)As(2)O(2) (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 ana logue, no evidence for either long- or short-range order was found over the 2 theta range investigated down to 4 K. The results of these characterizat ions are compared with those of the previously studied phase, Sr2Mn3As2O2.