Effects of Nanoparticle Size and Density on the Critical Current and Creep in (Y,Gd)BCO Films: Comparisons to Strong Pinning Theory*

Incorporating nanoparticle inclusions into superconducting films is a well-established route for boosting current carrying capacity. (Y,Gd)Ba₂Cu₃O₇ films containing various nanoparticles have been shown to demonstrate inexplicably slow rates of thermally activated vortex motion (creep, S). Understanding the microscopic source of these slow rates is key to determining how to reduce S in superconductors. In this project, we report on the effects of different sizes and densities of nanoparticle inclusions on the critical current and creep in (Y,Gd)Ba₂Cu₃O₇ films. Samples in this study all contain a low density of R₂Cu₂O₅ (R = Y,Ba) inclusions (naturally occurring during growth), and each contain either no other nanoparticles, BaHfO₃, BaSnO₃, or BaZrO₃ nanoparticles. The data presented was collected from low temperature magnetization measurements in fields of 0.3 T up to 35 T using a VSM at the NHMFL and a local commercial SQUID.