The irreversibility behavior of NdBaCuO fabricated by top-seeded melt processing

Abstract

Large, single grain NdBa2Cu3O7−δ (Nd123)–Nd4Ba2Cu2O10 (Nd422) composites have been fabricated up to 2 cm in diameter in a controlled 1% O2 in N2 atmosphere using a top-seeded melt growth technique. The irreversibility field as a function of temperature has been obtained from magnetic hysteresis loops for magnetic fields applied parallel and perpendicular to the c axis of small specimens (≈2×2×3 mm3) cut from individual grains. These specimens are observed to exhibit a pronounced peak effect for current flowing in the a–b plane and a five-fold anisotropy in the irreversibility line over a wide temperature range for fields applied along the major crystallographic axes. An exceptionally high irreversibility field (>12 T at 89 K) is observed in this material for field applied perpendicular to the c axis, which extrapolates to well over 40 T at 77 K.