Critical current density of YBa₂Cu₃O_y containing inclined columnar defects

Effects of columnar defects on the critical current density have been investigated by the in situ measurement of current-voltage characteristics for a c-axis oriented YBa₂Cu₃O_y (YBCO) thin film after the irradiation with 200 MeV Au ions from the direction θ_irr = 45° off the c-axis. The dependences of the critical current density, J_c, on the magnetic field, the magnetic field angle, and the density of columnar defects are discussed. With increasing the density of the columnar defects, B_φ, the contribution of the columnar defects to the pinning force per unit volume, ΔF_p, increases monotonically. The peak field for ΔF_p as a function of the magnetic field seems to be almost independent on B_φ.