Anisotropic, non-monotonic behavior of the superconducting critical current in thin YBa2Cu3O7-d films on vicinal SrTiO3 surfaces

TL;DR

This study investigates the anisotropic and non-monotonic behavior of the critical current in thin YBa2Cu3O7-d films on vicinal SrTiO3, revealing complex vortex interactions and strain effects influencing superconducting properties.

Contribution

It provides new insights into how vicinal substrate angles affect vortex pinning and critical current anisotropy in YBCO films, highlighting the role of anti-phase boundaries and strain.

Findings

Enhanced pinning along the longitudinal direction at low fields for certain vicinal angles.

Observation of a peak in Jc(H) due to vortex interactions.

Reversal of in-plane Jc anisotropy linked to substrate-induced strain.

Abstract

The critical current density of epitaxial YBCO films grown on vicinal SrTiO3 substrates was investigated by electrical transport measurements along and across the steps of the SrTiO3 surface for a range of temperatures of 10 K to 85 K and in applied magnetic fields varying from 0 to 14 T. For vicinal angles of 4 and 8 degrees, we found evidence of enhanced pinning in the longitudinal direction at low magnetic fields for a wide region of temperatures and attribute this phenomenon to anti-phase boundaries in the YBCO film. The transverse Jc data showed a peak in the Jc(H) curve at low magnetic fields, which was explained on the basis of magnetic interaction between Abrikosov and Abrikosov-Josephson vortices. The in-plane Jc anisotropy observed for vicinal angles of 0.4 degrees was reversed with respect to the 8 degree and 4 degree samples. This phenomenon was interpreted on the basis of strain induced in the YBCO film by the stepped substrate's surface.