Vortex dynamics in YBa2Cu3O7−δ with in-plane columnar defects introduced by irradiation

• Single crystals of YBa2Cu3O7−δ irradiated with heavy ions parallel to the ab-plane.
• Columnar defects suppress first order melting transition for H || ab.
• Columnar defects inhibit motion of vortices parallel to the defects.
• Irreversibility line shifts upward for H || ab and downward for H || c.
• Irradiation increases the pinning anisotropy.

We report on the effects of introducing columnar defects by irradiation in clean single crystals of YBa2Cu3O7−δ in a direction parallel to the ab-plane. The defects were introduced by bombarding the samples with 208Pb56+ ions at an energy of 1.4 GeV. We find that the defects suppress the first order melting transition for magnetic fields aligned parallel or at small angles relative to the defects. The columnar defects inhibit vortex motion of vortices parallel to the defects, while the vortices experience less pinning when they are perpendicular to the defects. Our results suggest that the pinning anisotropy is increased, at least for magnetic fields up to the matching field dose of 1 T.