Abstract
Polycrystalline samples of Sr2Mn2CuAs2O2, Sr2Mn3As2O2, and Sr2Zn2MnAs2O2 were synthesized.
Their temperature- and applied magnetic field-dependent structural, transport, thermal,
and magnetic properties were characterized by means of x-ray and neutron diffraction, electrical
resistivity ρ, heat capacity, magnetization and magnetic susceptibility measurements. These compounds
have a body-centered-tetragonal crystal structure (space group I 4/mmm) that consists of
MO2 (M = Zn and/or Mn) oxide layers similar to the CuO2 layers in high superconducting transition
temperature Tc cuprate superconductors, and intermetallic MAs (M = Cu and/or Mn) layers
similar to the FeAs layers in high-Tc pnictides. These two types of layers alternate along the crystallographic
c-axis and are separated by Sr atoms. The site occupancies of Mn, Cu and Zn were
studied using Rietveld refinements of x-ray and neutron powder diffraction data. The temperature
dependences of ρ suggest metallic character for Sr2Mn2CuAs2O2 and semiconducting character
for Sr2Mn3As2O2 and Sr2Zn2MnAs2O2. Sr2Mn2CuAs2O2 is inferred to be a ferrimagnet with a
Curie temperature TC = 95(1) K. Remarkably, we find that the magnetic ground state structure
changes from a G-type antiferromagnetic structure in Sr2Mn3As2O2 to an A-type ferrimagnetic
structure in Sr2Mn2CuAs2O2 in which the Mn ions in each layer are ferromagnetically aligned, but
are antiferromagnetically aligned between layers.
