Linear defects in epitaxial Y-Ba-Cu-O films: their role inanisotropic vortex pinning and microwave surface resistance

摘要

YBa2Cu3O7-δ films exhibit two orders of magnitude higher critical current density, Jc, and a few times higher microwave surface resistance, Rs, than single crystals. This evidences a different nature of crystal defects, which are responsible for the pinning and HF losses. Several types of dislocation arrays are identified in YBCO films by TEM/HREM and XRD. An analysis of Jc(H,T,θ) and Rs(T)-dependencies along with X-ray and HREM data for films grown via various modes allows to differentiate contributions to Jc and Rs from out-of-plane and in-plane edge dislocations. The higher the density of edge dislocations within YBCO film the higher are Jc and Rs. Stress-strain field calculations allow one to comprehend the difference between out-of-plane and in-plane dislocations effects