J D Moore et al 2009 Supercond. Sci. Technol. 22 125023 doi:10.1088/0953-2048/22/12/125023
J D Moore1, L F Cohen1, Y Yeshurun1,5, A D Caplin1, K Morrison1, K A Yates1, C M McGilvery2, J M Perkins2, D W McComb2, C Trautmann3, Z A Ren4, J Yang4, W Lu4, X L Dong4 and Z X Zhao4
Show affiliationsAn oxypnictide superconductor NdFeAsO0.85 sample with transition temperature of 46 K was irradiated with 2 GeV Ta ions at a fluence of 5 × 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.
74.25.Qt Vortex lattices, flux pinning, flux creep
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
Issue 12 (December 2009)
Received 30 June 2009, in final form 15 September 2009
Published 23 October 2009
J D Moore et al 2009 Supercond. Sci. Technol. 22 125023
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