Tuning critical current density properties of YBaCuOy thin films under longitudinal magnetic field by using heavy-ion irradiation

Sueyoshi, Tetsuro*; Enokihata, Ryusei*; Yamaguchi, Hiroshi*; Semboshi, Satoshi*; Ozaki, Toshinori*; Sakane, Hitoshi*; Nishizaki, Terukazu*; Ishikawa, Norito   

We attempted to improve the critical current density (Jc) under a longitudinal magnetic field (LMF) by using columnar defects (CDs) tilted toward the transport current, where the CDs were produced with 80 MeV Xe ions at an incident angle(s) up to 87.5 degree relative to the c-axis of YBaCuOy thin films. The formation of CDs extending throughout the film was confirmed by cross-sectional transmission electron microscopy. The CDs tilted at 87.5 degree weakened the magnetic field dependence of Jc under the LMF, providing a Jc higher than that of the unirradiated film in a high magnetic field. This is the first study to demonstrate that CDs and/or irradiation defects contribute to flux pinning under the LMF in high-Tc superconductors.