Enhanced vortex-pinning strength and magnetic-irreversibility via columnar defects in single crystal Bi₂Sr₂CaCu₂O₈

To enhance vortex pinning in the high-Tc superconductor Bi2Sr2CaCu2O8, single crystals were irradiated with energetic heavy ions to create columnar defects. Irradiations were made at various angles from the c-axis. The pinning energy U0 was investigated by ac magnetometry near B(Tirr), the limit of quasistatic magnetic irreversibility. Irradiation increased U0 by a factor of ∼3, relatively independent of the ion-beam exposure, which increased both Jc and the irreversible BT regime. Independence of Jc and U0 from the magnetic-field orientation suggests the predominance of strong pins interacting with 2-D pancake vortices. © 1994.