Superconducting Properties of (Mx/YBa2Cu3O7-delta y)N Multilayer Films with Variable Layer Thickness x (Postprint)
Abstract
The superconducting properties of (Mx /YBa2Cu3O7-dy)N multilayer films were studied for varying layer thickness x. Different M phases were examined including green-phase Y2BaCuO5 (211), Y2O3, BaZrO3, CeO2, SmBa2Cu3O7-d (Sm123), brown-phase La2BaCuO5 (La211), and MgO. Multilayer (Mx /YBa2 Cu3O7-dy)N structures were grown by pulsed laser deposition onto SrTiO3 or LaAlO3 single-crystal substrates by alternate ablation of separate YBa2-Cu3O7-d (123) and M targets, at temperatures of 750 deg C to 790 deg 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 (Tc), critical current density as a function of applied magnetic field Jc(H), self-field Jc(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 BaZrO3 at 65 to 77 K, Y2O3 at 65 K, and CeO2 for H < 0.5 T. BaZrO3 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 x 10(exp 11) nanoparticles/sq cm. To optimize flux pinning and Jc (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 Jc unexpectedly increased with increasing x layer thickness.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 2012
- Accession Number
- ADA561108
Entities
People
- A. L. Westerfield
- I. Brockman
- J. M. Evans
- M. F. Locke
- N. A. Pierce
- P. Klenk
- Paul N. Barnes
- Robert W. Morgan
- T. A. Campbell
- Timothy J. Haugan
Organizations
- Air Force Research Laboratory