Increased pinning energies and critical current densities in heavy-ion-irradiated Bi₂Sr₂CaCu₂O₈ single crystals

We report a significant increase in the pinning energy of vortices in single-crystal Bi₂Sr₂CaCu₂O₈ when irradiated with heavy ions such as Ar⁺. This is in contrast with the results of light ion (H⁺, He⁺) irradiations which give pinning energies comparable with those of unirradiated crystals. The stronger pinning is attributed to defects larger than point defects, e.g., clusters or amorphized regions. As a result of higher pinning energies, critical currents persist at markedly higher temperatures and fields.