Effect of magnetic field on resistive transition of thin film thallium based superconductors

The temperature and magnetic field dependencies of a.c. resistance of c-axis oriented (Tl0.5Pb0.5)(Sr0.8Ba0.2)2Ca2Cu3Ox and (Tl0.6Pb0.24Bi0.16)(Sr0.9Ba0.1)2Ca2Cu3Ox thin films as well as of (Tl0.5Pb0.5)(Sr0.8Ba0.2)2Ca2Cu3Ox bulk sample from 77 K to room temperature and in magnetic field from zero to 3000 Oe were measured and analyzed. The magnetic fields and temperature dependence of the resistive superconducting transition and irreversibility field were discussed both in the flux-creep model and in the superconducting liquid vortex state model. The temperature width of resistive transition was explained taking advantage of the Ambegaokar and Halperin model of the resistance of superconducting Josephson weak links and barrier of vortex motion presented by Tinkham. The irreversibility field was described by an exponential formula. (author)