Angularly Dependent, Contact-free Current Density Measurements of YBCO Coated Conductor

Studying the angular dependence of the current density $J$ gives insight into vortex pinning. We investigated a coated conductor of YBa$_{2}$Cu$_{3}$O$_{\sim 7}$ containing $c$-axis correlated defects (stacks of BaZrO$_{3}$ particles), striated into six strips to give a high aspect ratio. The current density was determined inductively from the magnetic moment $m\sim J$, using a SQUID magnetometer. The sample was mounted on a horizontal rotating platform to vary the angle $\theta $ of the sample with respect to the vertical applied magnetic field. The magnetometer allows us to measure both the longitudinal and transverse components of moment \textbf{m}($\theta )$, enabling calculation of the angular dependence of $J$. For a large range of applied magnetic fields at various temperatures, we found a pronounced peak in $J(\theta )$ at an angular value ($\theta _{peak})$ near the $c$-axis. We observed that, for a large range of applied magnetic fields, $\theta _{peak}$ linearly scales with 1/$h$, where $h$ = ($H$/$H_{c2})$ is the reduced field. Research sponsored by DOE, Division of Materials Sciences and Engineering, and Office of Electricity Delivery and Energy Reliability.