Extraction of anisotropic critical current densities and flux pinning potentials

Abstract

Magnetic measurements were performed on an MTG YBa 2Cu 3O 6+ x sample at three field orientations. An extended Bean model was used to extract the anisotropic critical current densities. Compared with the corresponding magnetic measurement at the H| ab plane, the anomalous increase of calculated J ab, ab (critical current density flowing in the ab plane at H ⊥ c-axis) with the applied field is much more clear, and its field dependence is similar to that of magnetization hysteresis at H| c-axis. Moreover, from the magnetization relaxation measurements at H| ab the time dependences of J ab, ab and J c, ab (critical currents flowing along the c-axis at H| ab plane) were derived and used to determine the two corresponding effective activation energies for flux motion. Both of the current density dependences can be fit with the power law but with different exponents, which may provide a possible explanation of the stronger temperature dependence of J ab, ab than J c, ab .