Comparison of the magnetic ordering in Sr₂Yb₁Ru _0.9Cu_0.1O₆ and Ru₁Sr ₂Gd₁Cu₂O₈ superconductors

Ru₁Sr₂Gd₁Cu₂O₈ and Sr₂Yb₁Ru_0.9Cu_0.1O₆ were synthesized using a solid-state reaction. X-ray diffraction showed that Ru ₁Sr₂Gd₁Cu₂O₈ crystallized into the tetragonal Ru-1212 structure (space group P4/mmm), whereas the Sr ₂Yb₁Ru_0.9Cu_0.1O₆ had a monoclynic structure (space group P2₁/n). Sr₂Yb ₁Ru_0.9Cu_0.1O₆ showed a possible magnetic transition (T _{m a g} ) at 44 K with a superconducting transition temperature T _c at 30 K. In contrast, Ru ₁Sr₂Gd₁Cu₂O₈ showed a magnetic transition at 140 K with a T _c at 25 K. The magnetization data for Sr₂Yb₁Ru_0.9Cu_0.1O ₆ 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 Sr₂Yb₁Ru_0.9Cu_0.1O ₆ superconductor.