Transport properties of heavy-ion irradiated YBa ₂Cu ₃Ox thin films

We studied the effect of heavy-ion irradiation on the transport properties of YBa ₂Cu ₃O _x thin films. The films were grown on LaAlO ₃ substrate by using laser ablation and were then irradiated by Sn ions with a dose equivalent to a 1-T vortex density. Half of the films was covered during irradiation so that direct comparison could be made. We found that the critical current density at 77 K increased after irradiation from 1.2 × 10 ⁵ to 1.8 × 10 ⁵ A/cm ² in a 2-T field. The irreversibility line also showed a large shift to higher temperatures. The Hall- effect measurement revealed that the scaling behavior between the longotudinal and Hall resistivities, as well as the behavior of the Hall conductivity, had been modified after the heavy-ion irradiation.