Direct observation of vortices trapped at stacking fault dislocations in Bi_2Sr_2CaCu_2O_8 by a low-temperature magnetic force microscope

摘要

We have studied the vortex structure in Bi_2Sr_2CaCu_2O_8 single crystal with low-density artificial columnar defects formed by the irradiation of 1.3 GeV uranium ions by using a low-temperature magnetic force microscope. We observed that some of the topographic steps are acting as strong line pinning centers for magnetic vortices in this material. We confirmed that these line steps correspond to the stacking fault dislocations. The stacking fault dislocation showed a direction dependent pinning behavior due to the line-shape geometry of the dislocation. The movement of the vortices across the dislocation line is impeded, while the movement along the dislocation line is quite free.