  Oxypnictide superconductor NdFeAsO0.85 sample was irradiated with 2 GeV Ta
ions at a fluence of 5x10^10 ions/cm2. High resolution transmission electron
microscopy study revealed that the irradiation produced columnar-like defects.
The effect of these defects on the irreversible magnetisation in
polycrystalline randomly oriented fragments was studied as a function of field
angle and field sweep rate. We find that the critical current density is
enhanced at fields below the matching field (~1 Tesla) but only marginally. The
pinning enhancement is anisotropic and maximum along the defect direction at
high temperatures but the pinning then becomes more isotropic at low
temperatures. The creep rate is suppressed at high temperatures and at fields
below the matching field, indicating the columnar defects are efficient pinning
sites at these H and T conditions.
