Magnetic properties of polycrystallineR1.5Ce0.5Sr2Cu2NbO10(R=Eu, Nd, and Sm) high-Tcsuperconducting ceramics

Abstract

Magnetic characterization has been performed on the superconducting members of the ${\mathit{R}}_{1.5}$${\mathrm{Ce}}_{0.5}$${\mathrm{Sr}}_{2}$${\mathrm{Cu}}_{2}$${\mathrm{NbO}}_{10}$ (R=Eu, Nd, and Sm) series. These materials are related to the ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ structure through the replacement of the CuO chains with ${\mathrm{NbO}}_{2}$ planes, and the single rare-earth elements with a ${\mathit{R}}_{2}$${\mathrm{O}}_{2}$ fluorite structure. Measurements of the lower critical-field curve, irreversibility line, volume fraction, Meissner fraction, and magnetic relaxation are reported for each compound. No evidence of intergrain weak-link behavior down to 0.1 Oe is observed. Estimates of the zero-field intragrain critical current density from high-field hysteresis curves taken at 6 K for the Nd-, Sm-, and Eu-based systems are 2.7\ifmmode\times\else\texttimes\fi{}${10}^{4}$, 3.3\ifmmode\times\else\texttimes\fi{}${10}^{4}$, and 4.7\ifmmode\times\else\texttimes\fi{}${10}^{4}$ A/${\mathrm{cm}}^{2}$, respectively.