Superconductivity Research Laboratory, International Superconductivity Technology Center, 10-13 Shinonome 1-chome, Koto-ku, Tokyo, 135, Japan
Abstract:
We have studied the superconducting properties of Nd(Ba1−xNdx)2Cu3O7−δ (Nd123, x ≈ 0.1) single crystals grown by the traveling-solvent floating-zone method under 0.1% O2 in Ar atmosphere. The enhancement of the magnetization with increasing field is observed in the hysteresis (M-H) loop in fields both parallel and perpendicular to the c-axis of the Nd123 single crystals as well as in the bulk crystals prepared by the oxygen-controlled-melt-growth (OCMG) method. The composition variation of Ba/Nd is observed in the matrix of Nd123 crystals by an analytical TEM equipped with a cold field-emission gun. It turns out that the enhancement is due to the field-induced pinning effect ascribed to the weak superconducting Nd---Ba substitution regions in the Nd123 matrix.