Angular dependence of<i>J</i>_cfor YBCO coated conductors at low temperature and very high magnetic fields

Abstract

We present very high field angle dependent critical current density (Jc) data for three recently obtained YBa2Cu3O7−x (YBCO) coated conductors used in the construction of high field solenoids. We find that strongly correlated pins, such as BaZrO3 (BZO) nanorods, while yielding strong c-axis peaks at 77 K, produce almost no measurable contribution at 4 K. Raising the field from <5 to 30 T at 4 K causes a marked transition from a Ginzburg–Landau-like Jc(θ) at low fields to a marked cusp-like behavior at high fields. Transmission electron micrographs show that all samples contain a high density of stacking faults which strengthen the plane correlated pinning parallel to the ab planes produced by the intrinsic ab-plane pinning of the Cu–O charge reservoir layers.