The Synthesis, Structure and Physical Properties of the Layered Ruthenocuprates RuSr2GdCu2O8 and Pb2Sr2Cu2RuO8Cl

Abstract

Studies of the structure and physical properties of the layered rutheno- cuprates RuSr2GdCu2O8 and Pb2Sr2Cu2RuO8Cl are reviewed. RuSr2GdCu2O8 is a weak ferromagnetic superconductor and doping studies have shown that it is possible to tune the magnetic and superconducting transitions simultaneously. The average crystal structure of RuSr2GdCu2O8 is tetragonal at both 10 and 295 K (space group P4/mmm), but a sq.root2a x sq.root2a x c superstructure resulting from coherent rotations of the RuO6 octahedra within subdomains of 50-200 ºA is observed by selected area electron distraction (SAED). The same tilts and rotations of the RuO6 octahedra are observed in semiconducting Pb2Sr2Cu2RuO8Cl, which has strikingly similar magnetic properties to RuSr2GdCu2O8. Antiferromagnetic order is observed in the 10 K neutron diffraction pattern with a Ru moment of 1.1(1) B, but a spin-flop transition is observed above a field of 0.5 T.