Superconductivity and Magnetic Properties of High-Pressure Oxygen Synthesized Ru_(1-x)Sr_2GdCu_(2+x)O(8-x) Compounds

摘要

We report on the new superconducting materials with the formula Ru_(1-x)Sr_2GdCu_(2+x)O_(8-z) that have been synthesized under high-pressure oxygen conditions. By changing the ratio between Ru and Cu in the compound we were able to increase the temperature of the superconducting transition up to 72 K for x=0.3 and 0.4. Reentrant dependencies of the magnetization found at low temperatures are qualitatively explained assuming a quasi two-dimensional character of the superconducting regions. The magnetic characteristics of these compounds are discussed and compared to the existing data on RuSr_2GdCu_2O_8 magnetic superconductor (T_c~(on)=45K, T_N=132K).