Flux pinning properties of splayed columnar defects ranging from B || c-axis to B || ab-plane in GdBCO coated conductors

摘要

GdBa_2Cu_3Oy (GdBCO) coated conductors were irradiated using 270 MeV Xe ions at crossing angles ±hi relative to the c-axis, in order to clarify the flux pinning properties of splayed columnar defects (splayed CDs) not only around B || c-axis, but also around B || ab-plane. For the splayed CDs with smaller θ_i (i.e. crossing around the c-axis), a single peak is observed around B || c-axis in the angular dependence of critical current density J_c, which are attributed to the splay effect by the crossed CDs. For the splayed CDs with larger θ_i (i.e. crossing around the ab-plane), on the other hand, two sharp J_c peaks emerge near two irradiation angles ±θ_i and the J_c at B || ab-plane indicates not a peak but a dip structure. With diminishing the crossing angles of CDs relative to ab-plane, the value of J_c at B || ab-plane build up with the dip structure remained. These results suggest that the splayed CDs contribute to the flux pinning around the ab-plane, but do not induce the splay effect at B || ab-plane.