Systematic Studies to Enhance Flux Pinning of (BaZrO3/YBa2Cu3O7-x)N Multilayer Thin Films for the Full Landscape of T = 30 K to 77 K

Abstract

The (M/YBa₂Cu₃O_7-x)_N multilayer thin film structure has been studied by many groups, and achieves different microstructures and artificial pinning centers that result in large variations of critical current density (J_c) for a large landscape space of T = 30–77 K, H_appl = 0–9 T and 0° ≤ H_appl(θ) ≤ 90°. Herein provides a wide-ranging optimization study of (BaZrO_3,y/YBa₂Cu₃O_7-x,z)_N multilayer films prepared by pulsed laser deposition with y,z layer thickness. Process parameters studied include YBa₂Cu₃O_7-x (YBCO) layer thickness from 3–300 nm, BaZrO₃ (BZO) layer thickness from 0.5-1.5 nm, and film growth temperature from 775–825 °C. Systematic results of critical transition temperature (T_c) and J_c(H,T,Θ) were plotted as function of YBCO layer thickness and BZO addition up to 16 volume % . Optimization of J_c(H,T,θ) was found to vary with process parameters from 30–77 K, for example at 77 K flux pinning was optimized for 825 °C process temperature. However, for 30 K operation temperature, flux pinning was much less sensitive to BZO+YBCO film parameters, and slightly optimized for 805 °C process temperature. For all H,T conditions studied, the J_c(H,T) values achieved a maximum peak for BZO = 8–12 volume % additions in close agreement with published models of flux pinning, and required BZO layer thickness < 0.6 nm.