Observations of suppression of static and dynamic disorder in Bi2.15Sr1.85CaCu2O8+delta crystals by columnar defects

Muon spin rotation and small angle neutron scattering measurements have bee n carried out on Bi2.15Sr1.85CaCu2O8+delta single crystals irradiated with fast heavy ions. The data give substantial evidence that even below the mat ching field, the positions of the vortices, in a plane perpendicular to the tracks, are not random. Furthermore, the crossover to a glassy vortex arra ngement, observed in the pristine material, is moved to higher fields. It i s shown that the presence of the columnar defects also strongly suppresses the thermal fluctuations of the vortices in comparison with the pristine ma terial.