  Polycrystalline samples of the layered iron arsenides Sr2CrO3FeAs and
Ba2ScO3FeAs were synthesized by high temperature solid state reactions and
their crystal structures determined by the X-ray powder diffraction. Their
structures are tetragonal (P4/nmm; Sr2CrO3FeAs: a = 391.12(1) pm, c =
1579.05(3) pm; Ba2ScO3FeAs: a = 412.66(5) pm, c = 1680.0(2) pm, Z = 2) and
isotypic to Sr2ScO3CuS. Iron arsenide layers are sandwiched between
perowskite-like oxide blocks and separated by ~1600 pm, which is much larger
compared to the 1111 iron arsenide superconductors. The bond length and angles
within the FeAs layers are adapted to the space requirements of the oxide
blocks. Measurements of the magnetic susceptibility and electrical resistivity
show no hint for a SDW-like anomaly in both compounds. Sr2CrO3FeAs shows
Curie-Weiss paramagnetism above 160 K with an effective magnetic moment of
3.83(3) muB in good agreement with the theoretical value of 3.87 muB for Cr3+.
Antiferromagnetic ordering was detected below TN ~ 31 K. 57Fe Moessbauer
spectra of Sr2CrO3FeAs show a single signal that broadens below the magnetic
ordering temperature due to a small transferred hyperfine field induced by the
magnetic ordering of the chromium atoms. 57Fe-Moessbauer spectra of Ba2ScO3FeAs
show single signals at 298, 77, and 4.2 K which are only subject to weak
quadrupole splitting.
