Ferromagnetic behavior of the Ru_1-xSr₂GdCu_2+xO_8±z system with 0.0 < x < 1.0, synthesized at ambient pressure

The Ru_1-xSr₂GdCu_2+xO_8±z system with x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.9 and 1.0 was studied by differential thermal analysis (DTA) in air in order to determine the temperature interval at which the formation of the RuSr₂GdCu₂O₈ (Ru-1212) compound should be formed. For DTA data, samples were prepared by the solid-state reaction method at ambient pressure between 940 deg. C and 1050 deg. C. From the X-ray powder diffraction (XRD) patterns it was observed that this system is isostructural to the Ru-1212 compound. In addition, a pure phase up to x = 0.4 was obtained. Studies by the Scanning Electron Microscopy (SEM) technique produced a particle size around 1-5 μm. The results of Transmission Electronic Microscopy (TEM) studies confirm the tetragonal unit cell in the Ru_1-xSr₂GdCu_2+xO_8±z system. The temperature dependence of the electrical resistivity of the samples with x = 0.1, 0.2 and 0.4 annealed in oxygen flux for 6, 12 and 41 h, at T = 960 deg. C, shows a semiconducting behavior. The AC magnetic susceptibility measurement indicates ferromagnetic behavior with T^Curie between 130 and 138 K