(Georgia Institute of Technology, 1995-08-14)
Thompson, J. R.; Paul, David; Wang, Z. L. (Zhong Lin); Kroeger, D. M.; Christen, D. K.
This work establishes the stability at elevated temperatures of columnar defects, artificially formed in the Bi-based cupric oxide superconductor Bi₂Sr₂Ca₁Cu₂O₈ for enhanced vortex pinning. Isochronal anneals, conducted in air, led to losses of critical current density in two stages. The defects were relatively stable up to ~ 550 °C, where second stage annealing began; above this, the pinning diminished rapidly. The recrystallization and loss of columnar defects were corroborated by transmission electron microscopy.
(Georgia Institute of Technology, 1995-03-20)
Lowndes, D. H.; Christen, D. K.; Klabunde, C. E.; Wang, Z. L. (Zhong Lin); Kroeger, D. M.; Budai, J. D.; Zhu, Shen; Norton, D. P.
Strong flux pinning and a pronounced asymmetric angular dependence of J[subscript c]([eta, theta]) have been discovered in YBa[subscript 2]Cu[subscript 3]O[subscript 7—chi] films grown on miscut, mosaic LaAlO[subscript 3] substrate surfaces. A new pinning peak, which at low fields is nearly as strong as the “intrinsic pinning,” is observed for magnetic field orientations between the c axis and the CuO[subscript 2] plane. Cross-section transmission electron microscopy reveals columnar growth defects (2–3 nm diameter) aligned near the c axis, in concentrations ~10[superscript 10] cm[subscript —2]. The results demonstrate that deliberately modified substrate surfaces may introduce technologically useful flux pinning in YBa[subscript 2]Cu[subscript 3]O[subscript 7—chi] films.