HIGH CRITICAL-CURRENT DENSITY OF ND(BA,ND)(2)CU3O7-DELTA SINGLE-CRYSTALS

We have studied the superconducting properties of Nd(Ba1-xNdx)(2)Cu3O7-delta(Nd123, x approximate to 0.1) single crystals grown by the traveling-solvent floating-zone method under 0.1% O-2 in Ar atmosphere. An anomalous peak effect in the magnetization hysteresis (M-B) loop is observed in the Nd123 single crystals as well as in the Nd123 bulk crystals prepared by the oxygen-controlled melt growth (OCMG) method. The critical current density (J(c)) of the Nd123 single crystals is 70 600 A/cm(2) in 1.0 T at 77 K for the applied field perpendicular to the a-b plane. Uniform flux density distribution with the same shape as the sample is observed in the field perpendicular to the a-b plane by the magneto-optical flux-density observation. Finely dispersed white regions in the dark-field image due to Nd substitutions for Ba are observed in the Nd123 matrix by the transmission electron microscopy. The high J(c) value of the Nd123 single crystals in the applied field is explained by the field-induced pinning centers caused by the Nd-Ba substitutions in the Nd123 matrix. (C) 1995 American Institute of Physics.