High Critical Current Density 4 MA/cm(2) in Co-Doped BaFe2As2 Epitaxial Films Grown on (La, Sr)(Al, Ta)O-3 Substrates without Buffer Layers

High critical current densities J(c) of 4 MA/cm(2) at 4 K were obtained in Co-doped BaFe2As2 (BaFe2As2:Co) epitaxial films grown directly on (La, Sr)(Al, Ta)O-3 substrates by pulsed laser deposition. Use of a highly pure target and improvement of film homogeneity were the critical factors to achieve the high J(c). The improved BaFe2As2:Co epitaxial films contained almost no Fe impurity and showed high crystallinity (crystallite tilt angle Delta omega = 0.5 degrees and twist angle Delta phi = 0.5 degrees) and a sharp superconducting transition with a width of 1.1 K. It is considered that these improvements resulted in the enhanced superconducting properties comparable to those of single crystals. (C) 2010 The Japan Society of Applied Physics