The effect of columnar defects on the pinning properties of NdFeAsO0.85 conglomerate particles

• Published in: Superconductor science & technology 2009-12, Vol.22 (12), p.125023-125023 (5)
• Main Authors: Moore, J D, Cohen, L F, Yeshurun, Y, Caplin, A D, Morrison, K, Yates, K A, McGilvery, C M, Perkins, J M, McComb, D W, Trautmann, C, Ren, Z A, Yang, J, Lu, W, Dong, X L, Zhao, Z X
• Format: Article
• Language: English
• ISSN: 0953-2048; 1361-6668
• DOI: 10.1088/0953-2048/22/12/125023

An oxypnictide superconductor NdFeAsO0.85 sample with transition temperature of 46 K was irradiated with 2 GeV Ta ions at a fluence of 5 X 1010 ions cm-2. High resolution transmission electron microscopy study revealed that the irradiation produced columnar-like defects. The effect of these defects on the irreversible magnetization 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 moderately enhanced at fields below the matching field (~1 T). The pinning enhancement is anisotropic and maximum along the defect direction at 35 K, but becomes more isotropic as the temperature is decreased. The creep rate is suppressed at 35 K and at fields below the matching field, indicating that the columnar defects are efficient pinning sites under these H and T conditions.