  Sr2Cr3As2O2 is composed of alternating square-lattice CrO2 and Cr2As2
stacking layers, where CrO2 is isostructural to the CuO2 building-block of
cuprate high-Tc superconductors and Cr2As2 to Fe2As2 of Fe-based
superconductors. Current interest in this material is raised by theoretic
prediction of possible superconductivity. In this neutron powder diffraction
study, we discovered that magnetic moments of Cr(II) ions in the Cr2As2
sublattice develop a C-type antiferromagnetic structure below 590 K, and the
moments of Cr(I) in the CrO2 sublattice form the La2CuO4 -like
antiferromagnetic order below 291 K. The staggered magnetic moment 2.19(4){\mu}
B /Cr(II) in the more itinerant Cr2As2 layer is smaller than
3.10(6){\mu}_B/Cr(I) in the more localized CrO2 layer. Different from previous
expectation, a spin-flop transition of the Cr(II) magnetic order observed at
291 K indicates a strong coupling between the CrO2 and Cr2As2 magnetic
subsystems.
