Combined effect of flux pinning by three-directional columnar defects in a field-angular region of high-Tc superconductors

Abstract

We investigated the combined effect of flux pinning by three-directional columnar defects (CDs) in a wide field-angular range of YBa2Cu3Oy thin films, where CDs parallel to the c-axis and CDs crossing at ±θi (θi = 45°, 60° and 80°) relative to the c-axis were installed by 200 MeV Xe-ion irradiations. The three-directional CDs with θi ≤ ±60° form a field angular curve of critical current density Jc with a broad peak centered at magnetic field (B) parallel to the c-axis, whereas the Jc shows no peaks around the crossing angles of ±θi. When the crossing angle is expanded to θi= ±80°, a drastic change in the field- angular behavior of Jc is induced: there is not a large enhancement of Jc around B || c, but two large peaks of Jc emerge at the two irradiation angles of θi= ±80°. We also demonstrated that the combined configuration consisting of CDs at θi = 0°, ±45°, ±60° and ±80° provides a uniform enhancement of Jc over a wide angular-region.