Critical currents of OCMG processed Nd123 crystals

Critical current densities of Nd123 crystals flux grown by the oxygen-controlled-melt-growth (OCMG) process have been studied with DC magnetization measurements. The superconducting transition temperature (T_c) of the Nd123 crystal flux grown in 0.1%O₂-Ar gas was 94 K with the applied field of 10 Oe parallel to the c-axis. The sample was found to be homogeneous without weakly linked regions through magneto-optical measurements. DC magnetization-hysteresis curves measured with a SQUID magnetometer exhibited a peak effect at various temperatures above 70 K. The peak effect is attributable to field-induced pinning by finely distributed low-T_c phases. The sample exhibited high critical current density (J_c) values of 4 × 10⁴ A/cm² in 2 T and over 1 × 10⁴ A/cm² in 4 T at 77 K for fields parallel to the c-axis.