Superconductivity in Ru(1-x)Sr2GdCu(2+x)O(8-y) Compounds

We report on the properties of new ruthenocuprates Ru(1-x)Sr2GdCu(2+x)O(8-y) (x=0, 0.1, 0.2, 0.3, 0.4, 0.75) that extend the superconductivity found previously in RuSr2GdCu2O8 (Tc=45 K) to the solid solution with varied Ru/Cu ratios. The compounds have been synthesized in high-pressure oxygen atmosphere. The maximum temperature of the superconducting transition is 72 K for the x=0.3 and 0.4 compositions. The reported behavior of magnetization at low temperatures can be qualitatively explained assuming a quasi-two-dimensional character of the superconducting regions in compounds studied.