Systematic enhancement of in-field critical current density with rare-earth ion size variance in superconducting rare-earth barium cuprate films

The strong systematic dependence of the in-field critical current density (J _c) on rare earth (RE) ion size variance in mixed RE-123 films was investigated. The average ionic radius was kept constant to remove the effect of the differing ionic radii. It was found that for a constant average RE ionic radius, there was a systematic dependence of the in-field J _c on the RE ion size variance with a small, but nonzero, variance being vaccum. It was also found that at 0.2T, samples with a non-zero variance on single crystal and IBAD-MgO substrates had higher J _c than YBCO by a factor of 2.