Anisotropy and lorentz-force dependences of critical current density in C-axis-oriented YBa₂Cu₃O_7-δ thin film

The magnetic field angular dependence of J_c(θ) for a c-axis-oriented YBa₂Cu₃O_7-δ (YBCO) thin film was measured using both constant and variable Lorentz force configurations. When the field was tilted from the c-axis within ±30°, J _c(θ) was independent of the intensity of the Lorentz force. This demonstrates that the vortices have bent segments trapped by pinning centers that extend parallel to the c-axis, and J_c(θ) is limited by the depinning of these segments. The effect on J_c(θ) of the two types of pinning centers, i.e., either parallel to the c-axis or to the ab plane, should be considered when the field is tilted from the ab plane within ±30°.