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Collomb D, Zhang M, Yuan W, Bending SJ. Imaging of Strong Nanoscale Vortex Pinning in GdBaCuO High-Temperature Superconducting Tapes. NANOMATERIALS (BASEL, SWITZERLAND) 2021; 11:1082. [PMID: 33922201 PMCID: PMC8145501 DOI: 10.3390/nano11051082] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 04/09/2021] [Accepted: 04/17/2021] [Indexed: 11/16/2022]
Abstract
The high critical current density of second-generation high-temperature superconducting (2G-HTS) tapes is the result of the systematic optimisation of the pinning landscape for superconducting vortices through careful engineering of the size and density of defects and non-superconducting second phases. Here, we use scanning Hall probe microscopy to conduct a vortex-resolved study of commercial GdBaCuO tapes in low fields for the first time and complement this work with "local" magnetisation and transport measurements. Magnetic imaging reveals highly disordered vortex patterns reflecting the presence of strong pinning from a dense distribution of nanoscale Gd2O3 second-phase inclusions in the superconducting film. However, we find that the measured vortex profiles are unexpectedly broad, with full-width-half-maxima typically of 6 μm, and exhibit almost no temperature dependence in the range 10-85 K. Since the lateral displacements of pinned vortex cores are not expected to exceed the superconducting layer thickness, this suggests that the observed broadening is caused by the disruption of the circulating supercurrents due to the high density of nanoscale pinning sites. Deviations of our local magnetisation data from an accepted 2D Bean critical state model also indicate that critical state profiles relax quite rapidly by flux creep. Our measurements provide important information about the role second-phase defects play in enhancing the critical current in these tapes and demonstrate the power of magnetic imaging as a complementary tool in the optimisation of vortex pinning phenomena in 2G-HTS tapes.
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Affiliation(s)
- David Collomb
- Department of Physics, University of Bath, Claverton Down, Bath BA2 7AY, UK;
| | - Min Zhang
- Applied Superconductivity Laboratory, Department of Electronics and Electrical Engineering, University of Strathclyde, Glasgow G1 1XQ, UK; (M.Z.); (W.Y.)
| | - Weijia Yuan
- Applied Superconductivity Laboratory, Department of Electronics and Electrical Engineering, University of Strathclyde, Glasgow G1 1XQ, UK; (M.Z.); (W.Y.)
| | - Simon J. Bending
- Department of Physics, University of Bath, Claverton Down, Bath BA2 7AY, UK;
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Talantsev EF, Strickland NM, Wimbush SC, Brooks J, Pantoja AE, Badcock RA, Storey JG, Tallon JL. The onset of dissipation in high-temperature superconductors: magnetic hysteresis and field dependence. Sci Rep 2018; 8:14463. [PMID: 30262898 PMCID: PMC6160411 DOI: 10.1038/s41598-018-32811-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 09/13/2018] [Indexed: 11/10/2022] Open
Abstract
Recently, we showed that the self-field transport critical current, Ic(sf), of a superconducting wire can be defined in a more fundamental way than the conventional (and arbitrary) electric field criterion, Ec = 1 μV/cm. We defined Ic(sf) as the threshold current, Ic,B, at which the perpendicular component of the local magnetic flux density, B⊥, measured at any point on the surface of a high-temperature superconducting tape abruptly crosses over from a non-linear to a linear dependence with increasing transport current. This effect results from the current distribution across the tape width progressively transitioning from non-uniform to uniform. The completion of this progressive transition was found to be singular. It coincides with the first discernible onset of dissipation and immediately precedes the formation of a measureable electric field. Here, we show that the same Ic,B definition of critical currents applies in the presence of an external applied magnetic field, Ba. In all experimental data presented here Ic,B is found to be significantly (10–30%) lower than Ic,E determined by the common electric field criterion of Ec = 1 µV/cm, and Ec to be up to 50 times lower at Ic,B than at Ic,E.
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Affiliation(s)
- E F Talantsev
- M.N. Mikheev Institute of Metal Physics, Ural Branch, Russian Academy of Sciences, 18, S. Kovalevskoy St, Ekaterinburg, 620108, Russia. .,NANOTECH Centre, Ural Federal University, 19 Mira St., Еkaterinburg, 620002, Russia.
| | - N M Strickland
- Robinson Research Institute, Victoria University of Wellington, 69 Gracefield Road, Lower Hutt, 5010, New Zealand
| | - S C Wimbush
- Robinson Research Institute, Victoria University of Wellington, 69 Gracefield Road, Lower Hutt, 5010, New Zealand.,The MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, P O Box 600, Wellington, 6140, New Zealand
| | - J Brooks
- Robinson Research Institute, Victoria University of Wellington, 69 Gracefield Road, Lower Hutt, 5010, New Zealand
| | - A E Pantoja
- Robinson Research Institute, Victoria University of Wellington, 69 Gracefield Road, Lower Hutt, 5010, New Zealand
| | - R A Badcock
- Robinson Research Institute, Victoria University of Wellington, 69 Gracefield Road, Lower Hutt, 5010, New Zealand
| | - J G Storey
- Robinson Research Institute, Victoria University of Wellington, 69 Gracefield Road, Lower Hutt, 5010, New Zealand.,The MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, P O Box 600, Wellington, 6140, New Zealand
| | - J L Tallon
- Robinson Research Institute, Victoria University of Wellington, 69 Gracefield Road, Lower Hutt, 5010, New Zealand.,The MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, P O Box 600, Wellington, 6140, New Zealand
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