Current redistribution of a current carrying superconducting tape in a perpendicular magnetic field

Abstract

The current redistribution of a high T(c) superconducting tape with increasing transport current in a magnetic field (H(a)) was visualized. The external magnetic field was applied normal to the surface of the sample after zero-field cooling, and the transport current (I(a)) was increased stepwise from 0 to 90% of the values of the critical current (I(c)(H(a))) at H(a). The field distribution near the sample surface across the tape width (2w) was measured using the scanning Hall probe method. Applying an inversion to the measured field distribution, we obtained the underlying current distribution. The initial fieldlike distribution was gradually changed into a currentlike distribution with an increase of the transport current. The transition occurred when Ia and Ha approached the line f = c in the f-c plane where f = I(a)/I(c) and c = tanh(H(a)/H(c)). H(c) is defined as I(c)/(2 pi w).