Observation of Structures of Chain Vortices Inside Anisotropic High-TcSuperconductors

In order to elucidate the formation mechanism of unconventional arrangements of vortices in high- $T_{\mathrm{c}}$ superconducting thin films at an inclined magnetic field to the layer plane, we investigated the structures of vortex lines inside the films by Lorentz microscopy using our 1-MV field-emission electron microscope. Our observation results concluded that vortex lines are tilted to form linear chains in ${\mathrm{YBaCu}}_3{\mathrm{O}}_{7,8}$. Vortex lines in the chain-lattice state in ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta }$, on the other hand, are all perpendicular to the layer plane, and therefore only vortices lined up along Josephson vortices form chains.