Magnetic losses, critical currents and pinning in coated conductors

The discovery of high temperature superconductors (HTS) in particular $YBa_{2}Cu_{3}O_{7-\delta}$ (YBCO) ($T_{c} \approx$ 92 K), sparked great interest in the use of HTS materials in practical applications such as transmission lines, motors and generators. Different techniques are used to fabricate these `coated conductors' from YBCO and other HTS. Ferromagnetic losses arise from the substrates that are used in the fabrication processes. I will talk about the studies we have done on these losses and also discuss the critical current ($J_c$) that flow in these coated conductors. On the other hand, exposing a type II superconductor to magnetic field generates vortices which are detrimental to the current carrying capabilities. These vortices have to be pinned (made immobile) in order to have significant and useful $J_c$ flow in these conductors. I will discuss the different pining mechanisms used in these coated conductors and particularly focus on the pinning features we studied on some set of YBCO thin films.