Superconducting properties of (M x /YBa 2Cu 3O 7-δy ) N multilayer films with variable layer thickness x

T. J. Haugan, P. N. Barnes, T. A. Campbell, N. A. Pierce, F. J. Baca, M. F. Locke, I. Brockman, A. L. Westerfield, J. M. Evans, R. Morgan, P. Klenk, B. C. Harrison, A. D. Chaney, I. Maartense

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Abstract

The superconducting properties of (M x /YBa 2Cu 3O 7-δy ) N multilayer films were studied for varying layer thickness x. Different M phases were examined including green-phase Y 2BaCuO 5 (211), Y 2O 3, BaZrO 3, CeO 2, SmBa 2Cu 3O 7-δ (Sm123), brown-phase La 2BaCuO 5 (La211), and MgO. Multilayer (M x /YBa 2 Cu 3O 7-δy ) N structures were grown by pulsed laser deposition onto SrTiO 3 or LaAlO 3 single-crystal substrates by alternate ablation of separate YBa 2Cu 3O 7-δ (123) and M targets, at temperatures of 750°C to 790°C. The x layer thickness was varied from 0.1 nm to 4.5 nm, and the y 123 layer thickness was kept constant within a given range of 10 to 25 nm. Different M phase and x layer thicknesses caused large variations of the microstructural and superconducting properties, including superconducting transition (T c), critical current density as a function of applied magnetic field J c(H), self-field J c(77 K), and nanoparticle layer coverage. Strong flux-pinning enhancement up to 1 to 3x was observed to occur for M additions of 211 and BaZrO 3 at 65 to 77 K, Y 2O 3 at 65 K, and CeO 2 for H < 0.5 T. BaZrO 3 had a noticeably different epitaxy forming smaller size nanoparticles ∼ 8 nm with 3 to 4x higher areal surface particle densities than other M phases, reaching 5 × 10 11 nanoparticles cm -2. To optimize flux pinning and J c (65 to 77 K, H = 2 to 3 T), the M layer thickness had to be reduced below a critical value that correlated with a nanoparticle surface coverage <15% by area. Unusual effects were observed for poor pinning materials including Sm123 and La211, where properties such as self-field J c unexpectedly increased with increasing x layer thickness.

Original languageEnglish (US)
Pages (from-to)1234-1242
Number of pages9
JournalJournal of Electronic Materials
Volume36
Issue number10
DOIs
StatePublished - Oct 1 2007

Keywords

  • Critical current density
  • Flux pinning
  • Magnetic field
  • Multilayer
  • Nanoparticle
  • Pulsed laser deposition
  • Superconductor
  • Thin film
  • YBa Cu O

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    Haugan, T. J., Barnes, P. N., Campbell, T. A., Pierce, N. A., Baca, F. J., Locke, M. F., Brockman, I., Westerfield, A. L., Evans, J. M., Morgan, R., Klenk, P., Harrison, B. C., Chaney, A. D., & Maartense, I. (2007). Superconducting properties of (M x /YBa 2Cu 3O 7-δy ) N multilayer films with variable layer thickness x. Journal of Electronic Materials, 36(10), 1234-1242. https://doi.org/10.1007/s11664-007-0229-y