Effect of Co substitution on superconductivity and magnetic order in RuSr2GdCu2O8

Samples of Ru1-xCoxSr2GdCu2O8 (x = 0, 0.01, 0.03, and 0.05) were synthesized by solid-state reaction. X-ray diffraction data indicate that all the samples are single phases with Ru-1212 structure. Rietveld refinement was carried out to determine the structure parameters. We present an investigation of the dc magnetic properties. The remnant magnetization at 5 K increases with the increasing of Co content, and the ferromagnetic ordering temperatures are slightly decreased with Co content increase. Substitution of Ru with Co suppresses superconductivity strikingly. The suppression of superconductivity is related to increasing ferromagnetic component in the RuO2 layers by Co doping and the decrease of the average (Ru,Co)-O bond length of (Ru,CO)O-6 octahedra. (C) 2003 Elsevier B.V. All rights reserved.