Second magnetization peak, anomalous field penetration, and Josephson vortices in KCa $$_2$$ 2 Fe $$_4$$ 4 As $$_4$$ 4 F $$_2$$ 2 bilayer pnictide superconductor
Abstract We performed magnetization measurements in a single crystal of the anisotropic bilayer pnictide superconductor KCa $$_2$$ 2 Fe $$_4$$ 4 As $$_4$$ 4 F $$_2$$ 2 , with $$T_c\;$$ T c $$\simeq$$ ≃ 34 K, for $$H$$ H $$\parallel$$ ‖ $$c$$ c -axis and $$H$$ H $$\parallel$$ ‖ $$ab$$ ab -planes. A s...
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Nature Portfolio
2022-11-01
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| Series: | Scientific Reports |
| Online Access: | https://doi.org/10.1038/s41598-022-24012-z |
| _version_ | 1811210820627988480 |
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| author | P. V. Lopes Shyam Sundar S. Salem-Sugui Wenshan Hong Huiqian Luo L. Ghivelder |
| author_facet | P. V. Lopes Shyam Sundar S. Salem-Sugui Wenshan Hong Huiqian Luo L. Ghivelder |
| author_sort | P. V. Lopes |
| collection | DOAJ |
| description | Abstract We performed magnetization measurements in a single crystal of the anisotropic bilayer pnictide superconductor KCa $$_2$$ 2 Fe $$_4$$ 4 As $$_4$$ 4 F $$_2$$ 2 , with $$T_c\;$$ T c $$\simeq$$ ≃ 34 K, for $$H$$ H $$\parallel$$ ‖ $$c$$ c -axis and $$H$$ H $$\parallel$$ ‖ $$ab$$ ab -planes. A second magnetization peak (SMP) was observed in the isothermal M(H) curves measured below 16 K for $$H$$ H $$\parallel$$ ‖ $$ab$$ ab -planes. A peak in the temperature variation of the critical current density, $$J_{c}$$ J c (T), at 16 K, strongly suggests the emergence of Josephson vortices at lower temperatures, which leads to the SMP in the sample. In addition, it is noticed that the appearance of Josephson vortices below 16 K renders easy magnetic flux penetration. A detailed vortex dynamics study suggests that the SMP can be explained in terms of elastic pinning to plastic pinning crossover. Furthermore, contrary to the common understanding, the temperature variation of the first peak field, $$H_1$$ H 1 , below and above 16 K, behaves non-monotonically. A highly disordered vortex phase, governed by plastic pinning, has been observed between 17 and 23 K, within a field region around an extremely large first peak field. Pinning force scaling suggests that the point defects are the dominant source of pinning for H $$\parallel$$ ‖ $$ab$$ ab -planes, whereas, for H $$\parallel$$ ‖ $$c$$ c -axis, point defects in addition to surface defects are at play. Such disorder contributes to the pinning due to the variation in charge carrier mean free path, $$\delta l$$ δ l -pinning. Moreover, the large $$J_c$$ J c observed in our study is consistent with the literature, which advocates this material for high magnetic field applications. |
| first_indexed | 2024-04-12T05:01:18Z |
| format | Article |
| id | doaj.art-5c15a481a8234e2687483126c061ef69 |
| institution | Directory Open Access Journal |
| issn | 2045-2322 |
| language | English |
| last_indexed | 2024-04-12T05:01:18Z |
| publishDate | 2022-11-01 |
| publisher | Nature Portfolio |
| record_format | Article |
| series | Scientific Reports |
| spelling | doaj.art-5c15a481a8234e2687483126c061ef692022-12-22T03:46:58ZengNature PortfolioScientific Reports2045-23222022-11-0112111010.1038/s41598-022-24012-zSecond magnetization peak, anomalous field penetration, and Josephson vortices in KCa $$_2$$ 2 Fe $$_4$$ 4 As $$_4$$ 4 F $$_2$$ 2 bilayer pnictide superconductorP. V. Lopes0Shyam Sundar1S. Salem-Sugui2Wenshan Hong3Huiqian Luo4L. Ghivelder5Instituto de Fisica, Universidade Federal do Rio de JaneiroInstituto de Fisica, Universidade Federal do Rio de JaneiroInstituto de Fisica, Universidade Federal do Rio de JaneiroBeijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of SciencesBeijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of SciencesInstituto de Fisica, Universidade Federal do Rio de JaneiroAbstract We performed magnetization measurements in a single crystal of the anisotropic bilayer pnictide superconductor KCa $$_2$$ 2 Fe $$_4$$ 4 As $$_4$$ 4 F $$_2$$ 2 , with $$T_c\;$$ T c $$\simeq$$ ≃ 34 K, for $$H$$ H $$\parallel$$ ‖ $$c$$ c -axis and $$H$$ H $$\parallel$$ ‖ $$ab$$ ab -planes. A second magnetization peak (SMP) was observed in the isothermal M(H) curves measured below 16 K for $$H$$ H $$\parallel$$ ‖ $$ab$$ ab -planes. A peak in the temperature variation of the critical current density, $$J_{c}$$ J c (T), at 16 K, strongly suggests the emergence of Josephson vortices at lower temperatures, which leads to the SMP in the sample. In addition, it is noticed that the appearance of Josephson vortices below 16 K renders easy magnetic flux penetration. A detailed vortex dynamics study suggests that the SMP can be explained in terms of elastic pinning to plastic pinning crossover. Furthermore, contrary to the common understanding, the temperature variation of the first peak field, $$H_1$$ H 1 , below and above 16 K, behaves non-monotonically. A highly disordered vortex phase, governed by plastic pinning, has been observed between 17 and 23 K, within a field region around an extremely large first peak field. Pinning force scaling suggests that the point defects are the dominant source of pinning for H $$\parallel$$ ‖ $$ab$$ ab -planes, whereas, for H $$\parallel$$ ‖ $$c$$ c -axis, point defects in addition to surface defects are at play. Such disorder contributes to the pinning due to the variation in charge carrier mean free path, $$\delta l$$ δ l -pinning. Moreover, the large $$J_c$$ J c observed in our study is consistent with the literature, which advocates this material for high magnetic field applications.https://doi.org/10.1038/s41598-022-24012-z |
| spellingShingle | P. V. Lopes Shyam Sundar S. Salem-Sugui Wenshan Hong Huiqian Luo L. Ghivelder Second magnetization peak, anomalous field penetration, and Josephson vortices in KCa $$_2$$ 2 Fe $$_4$$ 4 As $$_4$$ 4 F $$_2$$ 2 bilayer pnictide superconductor Scientific Reports |
| title | Second magnetization peak, anomalous field penetration, and Josephson vortices in KCa $$_2$$ 2 Fe $$_4$$ 4 As $$_4$$ 4 F $$_2$$ 2 bilayer pnictide superconductor |
| title_full | Second magnetization peak, anomalous field penetration, and Josephson vortices in KCa $$_2$$ 2 Fe $$_4$$ 4 As $$_4$$ 4 F $$_2$$ 2 bilayer pnictide superconductor |
| title_fullStr | Second magnetization peak, anomalous field penetration, and Josephson vortices in KCa $$_2$$ 2 Fe $$_4$$ 4 As $$_4$$ 4 F $$_2$$ 2 bilayer pnictide superconductor |
| title_full_unstemmed | Second magnetization peak, anomalous field penetration, and Josephson vortices in KCa $$_2$$ 2 Fe $$_4$$ 4 As $$_4$$ 4 F $$_2$$ 2 bilayer pnictide superconductor |
| title_short | Second magnetization peak, anomalous field penetration, and Josephson vortices in KCa $$_2$$ 2 Fe $$_4$$ 4 As $$_4$$ 4 F $$_2$$ 2 bilayer pnictide superconductor |
| title_sort | second magnetization peak anomalous field penetration and josephson vortices in kca 2 2 fe 4 4 as 4 4 f 2 2 bilayer pnictide superconductor |
| url | https://doi.org/10.1038/s41598-022-24012-z |
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