Structural state of second-generation HTSCs obtained by laser ablation

The structure of buffer layers and deposited YBa$_2$Cu$_3$O$_x$ (Y123) films with a high critical current density ($\sim$10$^6$ A/cm$^2$) has been investigated by different methods. These superconducting films and buffer layers are found to have a fine-grained structure, which, along with the high texture of Y123 films of the (001) type, is believed to be responsible for the high critical current density. An unusual texture is revealed in buffer layers, which differs from that of substrates and Y123 films. The superconducting films deposited on buffer CeO$_2$ layers exhibit a system of orthogonal lines; in the case under consideration, this is a manifestation of a domain structure with Y123 particles at boundaries.