Crystal growth and superconductivity of Fe-doped YBCO single crystals

Abstract Fe-doped YBa 2 Cu 3 O 7− δ (YBCO or Y123) single crystals have been grown using the SRL-CP crystal pulling technique for possible SNS junction applications. By varying Fe content in the liquid in the range of 0–3.73 mol%, the Cu sites substituted by Fe were found in the range of 0–5.45% and accordingly the k eff (effective Fe distribution coefficient) changed in the range of 0.35–0.75. The Fe interface composition in liquid C i is almost the same as the Fe bulk liquid composition C o , suggesting that interface kinetics is predominant and diffusion factor is negligible from the Fe solute point of view. The increasing substitution of Fe at Cu sites resulted in the decreasing trend of superconducting transition temperature ( T c ). It was found that the magnetization of the samples strongly depended on the annealing temperature. The reduction of T c was about 8.6 K/[Fe/(Fe+Cu)]% by annealing at 500°C, whereas about 4 K/[Fe/(Fe+Cu)]% by annealing at 420°C