Unique defect structure and advantageous vortex pinning properties in superconducting CaKFe4As4

Shigeyuki Ishida; Akira Iyo; Hiraku Ogino; Hiroshi Eisaki; Nao Takeshita; Kenji Kawashima; Keiichi Yanagisawa; Yuuga Kobayashi; Koji Kimoto; Hideki Abe; Motoharu Imai; Jun-ichi Shimoyama; Michael Eisterer

doi:10.1038/s41535-019-0165-0

arXiv · 1907.04718

Unique defect structure and advantageous vortex pinning properties in superconducting CaKFe4As4

Shigeyuki Ishida·Akira Iyo·Hiraku Ogino·Hiroshi Eisaki·Nao Takeshita·Kenji Kawashima·Keiichi Yanagisawa·Yuuga Kobayashi·Koji Kimoto·Hideki Abe·Motoharu Imai·Jun-ichi Shimoyama·Michael Eisterer

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Abstract

The lossless current-carrying capacity of a superconductor is limited by its critical current density (Jc). A key to enhance Jc towards real-life applications is engineering defect structures to optimize the pinning landscape. For iron-based superconductors (IBSs) considered as candidate materials for high-field applications, high Jc values have been achieved by various techniques to introduce artificial pinning centres. Here we report extraordinary vortex pinning properties in CaKFe4As4 (CaK1144) arising from the inherent defect structure. Scanning transmission electron microscopy revealed the existence of nanoscale intergrowths of the CaFe2As2 phase, which is unique to CaK1144 formed as a line compound. The Jc properties in CaK1144 are found to be distinct from other IBSs characterized by a significant anisotropy with respect to the magnetic field orientation as well as a remarkable pinning mechanism significantly enhanced with increasing temperature. We propose a comprehensive explanation of the Jc properties based on the unique intergrowths acting as pinning centres.

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Shigeyuki Ishida, Akira Iyo, Hiraku Ogino, Hiroshi Eisaki, Nao Takeshita, Kenji Kawashima, Keiichi Yanagisawa, Yuuga Kobayashi, Koji Kimoto, Hideki Abe, Motoharu Imai, Jun-ichi Shimoyama, Michael Eisterer. 2019-07-10. Unique defect structure and advantageous vortex pinning properties in superconducting CaKFe4As4. https://doi.org/10.1038/s41535-019-0165-0

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