Superconducting onset temperatures Tc up to 23-44 K are reported for the new RuCa2RCu2O8+δ (R = Pr, Nd, Sm, Eu, Gd) system with a Ru-1212 RuCa2PrCu2O 8+δ-type structure. Preliminary study indicates that the crystal structure is an orthorhombic distortion of the tetragonal RuSr 2GdCu2O8+δ-type structure, which has space group P4/mmm, Tm ∼ 136 K, and Tc(max) ∼ 65 K. With similar RuO6 octahedral and CuO5 pyramidal units, superconductivity from the Cu-O bi-layers apparently coexists with the weak ferromagnetic (WFM) order with magnetic ordering temperature Tm ∼ 49 K. Low temperature anomalous in magnetic properties observed in both field-cooled (FC) and zero-field-cooled (ZFC) modes are closely related to the complex interplay and coexistence between weak ferromagnetic order and superconductivity as well as from structural distortion and sensitive sample oxygen concentration variation. No superconductivity or Ru-1212 structure can be detected for larger rare earth compounds R = La and Ce.
All Science Journal Classification (ASJC) codes
- Statistical and Nonlinear Physics
- Condensed Matter Physics