Imaging of Strong Nanoscale Vortex Pinning in GdBaCuO High-Temperature Superconducting Tapes.
Imaging of Strong Nanoscale Vortex Pinning in GdBaCuO High-Temperature Superconducting Tapes.
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DOI：
10.3390/nano11051082
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发表时间：
2021-04-22
期刊：
影响因子：
--
通讯作者：
Bending SJ
中科院分区：
文献类型：
--
作者：
Collomb D;Zhang M;Yuan W;Bending SJ
第二代高温超导（2G-HTS）带的高临界电流密度是通过对缺陷和非超导第二相的尺寸和密度进行精心设计，系统优化超导涡旋钉钉景观的结果。在这里，我们首次使用扫描霍尔探针显微镜对低场下的商用GdBaCuO磁带进行了涡分辨研究，并通过“局部”磁化和输运测量来补充这项工作。磁成像显示了高度无序的涡流模式，反映了超导膜中密集分布的纳米级Gd2O3第二相夹杂物的强钉钉作用。然而，我们发现测量的涡廓出乎意料地宽，全宽半最大值通常为6 μm，并且在10-85 K范围内几乎没有温度依赖性。由于被钉住的涡旋核的横向位移预计不会超过超导层厚度，这表明所观察到的增宽是由于纳米级钉住点的高密度导致循环超电流中断造成的。我们的局部磁化数据与公认的二维Bean临界状态模型的偏差也表明，临界状态曲线由于磁流变而迅速松弛。我们的测量结果提供了关于第二相缺陷在提高这些磁带中的临界电流中所起作用的重要信息，并证明了磁成像作为优化2G-HTS磁带中涡流钉钉现象的补充工具的力量。
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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