Lorentz microscopy observation of vortices inside Bi-2212 thin films with columnar defects

We observed the arrangements of vortex lines inside Bi2Sr2CaCu2O8+delta (Bi-2212) thin films with tilted columnar defects by using Lorentz microscopy with our 1 MV holography electron microscope, It was found that while vortex lines were trapped along tilted columnar defects irrespective of the direction of the applied magnetic field at temperatures above 19 K. vortex lines stood up perpendicularly to the film plane below 12 K. This unusual behavior of vortices was attributed to the different pinning mechanism due to densely distributed atomic-size defects in Bi-2212. (C) 2001 Elsevier Science B.V. All rights reserved.