Magnetic characterization of rare-earth barium cuprate superconductors

Abstract

We report magnetic characterization of barium rare-earth cuprate superconductors to determine critical current densities as a function of rare-earth constituent. A vibrating sample magnetometer was used to measure $M-H$ loops for fields to 15 kOe of oriented single crystals. Critical current densities are insensitive to rare-earth constituent despite the magnetic moment on the rare-earth ion. Values of critical current densities in the $a-b$ plane vary from ∼3×${10}^5$ A/${\mathrm{cm}}^2$ at 10 K to ∼2×${10}^4$ A/${\mathrm{cm}}^2$ at 77 K. Anisotropy in the critical current density in the $a-b$ plane and perpendicular to this plane was a factor of 2 in a ${\mathrm{Ba}}_2$Yb${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ crystal at $T=38\mathrm{}$ K. Aluminum impurities lower critical currents but also reduce the superconducting transition temperature.