Flux-pinning Properties and Microstructure in SmBa_2Cu_3O_y Thin Films with BaZrO_3 Nanorods

Abstract

Self-organized BaZrO3 (BZO) nanorods in REBa2Cu3Oy superconducting films are known as promising artificial pinning centers. Previously, we have reported high-Jc Sm1+xBa2-xCu3Oy (SmBCO) films fabricated by a low-temperature growth (LTG) technique. The LTG technique expands the range of the deposition temperature in which the REBCO films show c-axis orientation, and makes it possible to control the crystal grain size and number density. In this study, in order to tune the pinning properties, we fabricated SmBCO films with BZO nanorods (LTG-SmBCO + BZO films) using the LTG technique and investigated the influence of the LTG technique on the growth of BZO nanorods and pinning properties in SmBCO films. With decreasing deposition temperature of the upper layer in the LTG-SmBCO + BZO films, the diameter of the films was decreased and the number density of BZO nanorods was increased, producing a high matching field, Bφ. Additionally, remarkable upturn shifts in the irreversibility field line and plateau regions in the magnetic-field dependence of Jc were observed in the range of Bφ/3 B Bφ. These results indicate that the nature of the Bose-glass-like state of vortices localized on c-axis-correlated pinning centers emerges in the range of Bφ/3 B Bφ.