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 I_a and H_a 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/(2πw).

Print publication: Issue 12 (December 2009)
Received 4 August 2009
Published 23 October 2009