Tuning the pinning energy in layered superconductors

Reversible magnetization measurements show that the pinning energy of vorti ces localized on amorphous tracks created in Bi2Sr2CaCu2O8 single crystals by heavy-ion irradiation can be adjusted by altering the irradiation angle. The pinning energy is found to be proportional to the. cross-sectional are a of the defects in the CuO2 planes. Both this size dependence and the obse rved quadratic temperature dependence of the pinning energy imply a predomi nant vortex core pinning interaction of pancake vortices with columnar defe cts as opposed to an electromagnetic pinning mechanism. An independent dete rmination of the value of the Ginzburg-Landau coherence length is also pres ented. [S0163-1829(99)00321-5].