Decoration of Josephson vortices by pancake vortices in ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+d}$

Josephson vortices are imaged magneto-optically due to their decoration with pancake vortices in ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+d}$ single crystals. Peculiarities of interaction between the pancake and Josephson vortices (JV) depending on the values of crossing fields and temperature are studied based on the observations of these decoration patterns. Evidence of the period-doubling in the decoration patterns compared to the JV stack period, migration of JV lines between neighboring stacks, and transitions between different JV configurations is reported. Imaging of the pancake/Josephson vortex decoration patterns over large areas is shown to be a sensitive tool for detecting local variations of the anisotropy and mapping imperfections in layered high-temperature superconductors.