Nondestructive determination of current–voltage characteristics of superconducting films by inductive critical current density measurements as a function of frequency

A nondestructive inductive method was developed to determine the current–voltage characteristics of superconducting films by measuring the critical current density Jc as a function of the frequency of ac magnetic fields. In well-known inductive methods that measure the Jc distribution of large-area films, Jc is measured at a frequency and the electric field E induced in the superconductor is proportional to the frequency; therefore, the E versus current density relation can be determined by measuring Jc at various frequencies. Current–voltage characteristics of YBa2Cu3O7 films measured by this method agree well with those determined by measuring magnetic-field-sweep rate dependence of magnetization.