Magnetization and transport properties in the superconducting Pr2Ba4Cu7O15−δ with metallic double-chain

Abstract We have reported the effect of pressure on the magnetization, and transport properties in the nominal composition Pr 2 Ba 4 Cu 7 O 15− δ synthesized by a sol–gel technique. A reduction treatment of the as-sintered sample in vacuum causes higher superconductivity achieving T c , on  = ∼30 K for δ  = 0.94. Application of hydrostatic pressure on the oxygen depleted sample enhances its onset temperature up to 36 K at 1.2 GPa, indicating the nearly optimum doping level of the charge carrier in comparison to the pressure dependence of lower T c samples with δ  = 0.45. Seebeck coefficient of the superconducting sample shows a metallic conduction, followed by a clear drop below T c , on and is in its temperature dependence below 100 K quite different from that of the non-superconducting one. This finding strongly suggests a dramatic change of the electronic state along the CuO double chain due to the reduction treatment for the appearance of superconductivity.