Comparison of the Magnetic Ordering in Sr2Yb1Ru0.9Cu0.1O6 and Ru1Sr2Gd1Cu2O8 Superconductors

Ru1Sr2Gd1Cu2O8 and Sr2Yb1Ru0.9Cu0.1O6 were synthesized using a solid-state reaction. X-ray diffraction showed that Ru1Sr2Gd1Cu2O8 crystallized into the tetragonal Ru-1212 structure (space group P4/mmm), whereas the Sr2Yb1Ru0.9Cu0.1O6 had a monoclynic structure (space group P21/n). Sr2Yb1Ru0.9Cu0.1O6 showed a possible magnetic transition ( T m a g ) at 44 K with a superconducting transition temperature T c at 30 K. In contrast, Ru1Sr2Gd1Cu2O8 showed a magnetic transition at 140 K with a T c at 25 K. The magnetization data for Sr2Yb1Ru0.9Cu0.1O6 suggests that this sample exhibits antiferromagnetic ordering in zero-field-cooled (ZFC) magnetization, whereas it reveals a weak ferromagnetic component during field-cooled (FC) cycles. In addition, larger diamagnetic signals were observed during FC cycle compared to the ZFC. These results suggest that the valence state of the Yb ion have a significant effect on the magnetic state of the Sr2Yb1Ru0.9Cu0.1O6 superconductor.