Influence of Irradiation-Induced Latent Tracks on Local Flux Pinning in Bi-2212 Crystals

For the first time the influence of irradiation-induced columnar defects (0.5 GeV I-ions) on flux line pinning in Bi-2212 crystals has been investigated by means of the high-resolution magneto-optical Faraday effect. By irradiating only a part of each sample, the local change in the flux pinning has been determined. Irradiated and nonirradiated parts have been investigated simultaneously under the same experimental conditions. At T = 5 K and μ 0 H ext = (0 ÷ 300) mT a large enhancement of j c, m is found in the irradiated region. The observation of the time dependence of the flux density distribution yields small values for the pinning potential U , supporting the model of two-dimensional pancake vortex pinning.