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L. Ya. Vinnikov , 1 I. S. Veshchunov, 1 T. M. Artemova, 1 M. R. Eskildsen 2 J. M. Densmore, 2

Vortex Structure in Superconducting Iron Pnictide Single Crystals. L. Ya. Vinnikov , 1 I. S. Veshchunov, 1 T. M. Artemova, 1 M. R. Eskildsen 2 J. M. Densmore, 2 T. D. Blasius, 3 C. D. Dewhurst, 4 N. Ni, 5 A. Kreyssig, 5 S. L. Bud'ko, 5 P. C. Can fi eld, 5 and A. I. Goldman 5

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L. Ya. Vinnikov , 1 I. S. Veshchunov, 1 T. M. Artemova, 1 M. R. Eskildsen 2 J. M. Densmore, 2

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  1. Vortex Structure in Superconducting Iron Pnictide Single Crystals • L. Ya. Vinnikov,1 • I.S. Veshchunov,1 T. M. Artemova,1 • M. R. Eskildsen2J. M. Densmore,2 • T. D. Blasius,3 • C. D. Dewhurst,4 • N. Ni,5 A. Kreyssig,5 S. L. Bud'ko,5 P. C. Canfield,5 and A. I. Goldman5 • J.Karpinski6 , N.Zhigadlo6 • A.Boris7 P. Popovich,7D. L. Sun,7 C. T. Lin, 7 • 1 Institute of Solid State Physics RAS, Chernogolovka, Moscow Region, 142432, Russia • 2 Department of Physics, University of Notre Dame, Notre Dame, IN 46556 USA • 3Physics Department, University of Michigan, Ann Arbor, MI 48109 • 4 Institut Laue-Langevin, 6 Rue Jules Horowitz, F-38042 Grenoble, France • 5 Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA • Laboratory for Solid State Physics, ETH, Zurich, Switzerland • Max Planck Institute for Solid State Research Stuttgart, Germany • Schegolev Memorial Conference Chernogolovka 2009

  2. *Crystal Structures of pnictides 122 1111 , single crystals *Motivation * Method * Vortices in BaFe1.8Co0.2As2 single crystals (Decoration, SANS, STM) *Vortex structure in K doped Ba1-xKxFe2As2 single crystals * Vortex structure in Sr1-xKxFe2As2 &SmFeAsO1-xFy single crystals * DISCUSSION Comparision with others single crystals LuNi2B2C, MgB2 ,BSCCO, YBa2Cu4O8, organic superconductor Strong pinning *Summary Outline

  3. Marianne Rotter, Michael Pangerl, Marcus Tegel and Dirk Johrendt Cond-mat :0807.4096 <<1111>> <<112>>

  4. *A new family of high-Tc superconductors -iron pnictides, Y.Kamihara et al (2008) 112 - BaFe1.8Co0.2As2 , (changes in”superconducting” FeAs layers) Ba1-xKxFe2As2 (changes in”insulating” BaK layers) 1111- SmFeAsO1-xFy *Comparison with vortex structures others single crystals A high critical current for single crystal (~106 A/cm2) Pinning centers , ξ cogerence length MOTIVATION

  5. BaFe1.8Co0.2As2 AmesLab, USA ReNi2B2C Re(Lu,Er,Ho) SmFeAsO1-xFy , ETH, Switzerland MgB2 Sr1-xKxFe2As2 MPI, Germany Ba1-xKxFe2As2 Bi2Sr2Ca1Cu2O (BSCCO) ISSP, Russia Single crystals:

  6. *Crystal Structures of pnictides 122 1111 , single crystals * Method * Vortices in BaFe1.8Co0.2As2 single crystals (Decoration, SANS, STM) *Vortex structure in K doped Ba1-xKxFe2As2 single crystals * Vortex structure in Sr1-xKxFe2As2 &SmFeAsO1-xFy single crystals * DISCUSSION Outline

  7. Sketch illustrating the main idea of the decoration method (Trauble and Essmann) PPN-2009

  8. Size distribution of Fe decoration particles. N-number of Fe particles on the scanned area of 2µm2.He gas pressure was ~2x10-2 Torr. The high resolution of about 100 nm of Bitter decoration techniqueis due to the small size of the magnetic particles (the average size is less than 10 nm).

  9. *Crystal Structures of pnictides 122 1111 , single crystals * Method * Vortices in BaFe1.8Co0.2As2 single crystals (Decoration, SANS, STM) *Vortex structure in K doped Ba1-xKxFe2As2 single crystals * Vortex structure in Sr1-xKxFe2As2 &SmFeAsO1-xFy single crystals * DISCUSSION Outline

  10. Vortices in BaFe1.8Co0.2As2 single crystals at magnetic field H=10 Oe NN-NN-2009

  11. Vortices in BaFe1.8Co0.2As2 single crystals at magnetic field H=40 Oe

  12. Vortices in BaFe1.8Co0.2As2 single crystals at magnetic field H=40 Oe NN-NN-2009

  13. Vortices in BaFe1.8Co0.2As2 single crystals at magnetic field H=40 Oe with Delaunay triangulation

  14. Distorted vortex lattices in BaFe1.8Co0.2As2 single crystals at magnetic field H=80 Oe 2mkm

  15. Vortices in BaFe1.8Co0.2As2 single crystals at magnetic field H=320 Oe

  16. Vortices in BaFe1.8Co0.2As2 single crystal near the edge at magnetic field H=40 Oe

  17. The SANS vortexdiffraction patterns were obtained at 2 K and applied fields of 810 (a), 740 (b), 630 (c) and 450 mT (d), M.R. Eskildsen et al , PRB 79 100501 (R) March 2009 BaFe1.8Co0.2As2

  18. Scanning Tunneling Spectroscopy and Vortex Imaging in the Iron-Pnictide Superconductor BaFe1:8Co02As2 Yi Yin, M. Zech, T. L. Williams, X. F. Wang, G. Wu, X. H. Chen & J. E. Hoffman arXiv: 0810 v1[cond-mat. Supr-con] 6 Oct 2008 В интервале 0.001 – 9 Tне наблюдается упорядоченная вихревая решетка 100 nm

  19. *Crystal Structures of pnictides 122 1111 , single crystals * Method * Vortices in BaFe1.8Co0.2As2 single crystals (Decoration, SANS, STM) *Vortex structure in K doped Ba1-xKxFe2As2 single crystals * Vortex structure in Sr1-xKxFe2As2 &SmFeAsO1-xFy single crystals * DISCUSSION Outline

  20. Vortices in Ba1-xKxFe2As2 single crystals at magnetic field H=10 Oe (G19 x=0.2)

  21. Vortices in Ba1-xKxFe2As2single crystals (G17,x=0.4;Sn-flux) at magnetic field H=20 Oe

  22. Vortices in BSCCO single crystals at magnetic field H=20 Oe

  23. Vortices in Ba1-xKxFe2As2 single crystals at magnetic field H=110 Oe (G41e ,x=0.35,selfflux) Tc =38K) Ba1-KxFe2As2 BSCCO (2212)

  24. Vortices in Ba1-xKxFe2As2 single crystals at magnetic field H=160 Oe (G41e ,x=0.35, Tc =38K) BSCCO (2212) Ba1-KxFe2As2

  25. *Crystal Structures of pnictides 122 1111 , single crystals * Method * Vortices in BaFe1.8Co0.2As2 single crystals (Decoration, SANS, STM) *Vortex structure in K doped Ba1-xKxFe2As2 single crystals * Vortex structure in Sr1-xKxFe2As2 &SmFeAsO1-xFy single crystals * DISCUSSION Outline

  26. Vortices in Sr1-xKxFe2As2 single crystals (G15, x=0.08, Tc=32K) at magnetic field H=46 Oe

  27. Vortices in SmFeAsO1-xFysingle crystals at magnetic field 46 Oe

  28. *Crystal Structures of pnictides 122 1111 , single crystals *Motivation * Method * Vortices in BaFe1.8Co0.2As2 single crystals (Decoration, SANS, STM) *Vortex structure in K doped Ba1-xKxFe2As2 single crystals * Vortex structure in Sr1-xKxFe2As2 &SmFeAsO1-xFy single crystals * DISCUSSION Comparision with others single crystals LuNi2B2C, MgB2 ,BSCCO, YBa2Cu4O8, organic superconductor Strong pinning *Summary Outline

  29. LuNi2B2C

  30. Vortices in MgB2

  31. MgB2 at small magnetic field (He=9 Oe) near the edge of the crystal

  32. Flux Line Lattice destruction by columnar defects in BSCCO

  33. Observation flux Line Lattice in the Organic Superconductors

  34. *Crystal Structures of pnictides 122 1111 , single crystals *Motivation * Method * Vortices in BaFe1.8Co0.2As2 single crystals (Decoration, SANS, STM) *Vortex structure in K doped Ba1-xKxFe2As2 single crystals * Vortex structure in Sr1-xKxFe2As2 &SmFeAsO1-xFy single crystals * DISCUSSION Comparision with others single crystals LuNi2B2C, MgB2 ,BSCCO, YBa2Cu4O8, organic superconductor Strong pinning *Summary Outline

  35. Jc (H)BaFe1.8Co0.2As2

  36. N.Ni et al arXiv:0811.1767

  37. SmFeAs O1-xFy single crystals Zhigadlo et al J. Phys. Cond. Matter 20 (2008) 342 202

  38. Computing the average area associated with each vortex we find a magnetic flux per vortex of 2.1±0.1 x10-7 G sm2 in perfect agreement with theoretical φ0= hc/2e. Highly distorted vortex lattices were revealed in BaFe1.8Co0.2As2 single crystals at magnetic fields 10- 320 Oe by high resolution decoration method (Bitter technique) as well as in SmFeAsO1-xFy Sr1-xKxFe2As2 and Ba1-xKxFe2As2 single crystals . We have revealed the disordered vortex structure in the single crystals of a new family of high-temperature superconductors based on layered compounds, iron pnictides, which is independent of the crystal structure type, doping, and synthesis methods. This allows us to conclude that the intrinsic mechanism of the vortex pinning of unclear nature exists in the iron pnictide single crystals. Summary

  39. The question is : are there distorted vortex lattice in iron pnictides because we have “bad” (with many defects) single crystals (trivial pinning)? Or absence of the regular vortex lattice in single crystals are attributed to strong intrinsic pinning related to magnetic or structural features Fe-As layers ?

  40. BSCCO (2212) Ba1-KxFe2As2

  41. Ba1-xKx Fe2As2 J.T. Park et al arXiv:0811.2224

  42. Vortices in BaFe1.8Co0.2As2 single crystals at magnetic field H=40 Oe

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