Determination of London penetration depth from ac susceptibility measurements of a square superconducting thin film

A technique is developed for determining the London penetration depth by ac susceptibility measurements of a square film. It is based on the numerical calculation of the Meissner susceptibility of square superconducting films as a function of the Pearl length and the critical-state susceptibility of thin disks previously derived analytically. With this technique, intrinsic superconducting properties may be studied for each film together with critical-current density. The application of the technique to an actual YBa2Cu3O7 (delta) film allows us to obtain its temperature dependent penetration depth and depairing current density. (C) 2014 Elsevier B. V. All rights reserved.