Journal of Low Temperature Physics

, Volume 178, Issue 3–4, pp 188–199 | Cite as

Flux Dynamics, ac Losses, and Activation Energies in (Ba\(_{0.6}\)K\(_{0.4})\)Fe\(_{2}\)As\(_{2}\) Bulk Superconductor

  • M. Nikolo
  • X. Shi
  • E. S. Choi
  • J. Jiang
  • J. D. Weiss
  • E. E. Hellstrom


Flux pinning and thermally assisted flux flow are studied in a (Ba\(_{0.6}\)K\(_{0.4})\)Fe\(_{2}\)As\(_{2}(T_\mathrm{c}\)=38.3 K) bulk samples in magnetic fields up to 18 T via ac susceptibility measurements. Ac susceptibility curves shift to higher temperatures as the frequency is increased from 75 to 1,997 Hz in all fields. The frequency (\(f)\) shift of the susceptibility curves is modeled by the Anderson-Kim Arrhenius law \(f = f_{0}\mathrm{exp}(-E_\mathrm{a}{ /kT})\) to determine flux activation energy \(E_\mathrm{a}/k\) as a function of ac field \(H_\mathrm{ac}\) and dc magnetic flux density \(\mu \) \(_\mathrm{0} H_\mathrm{dc}\). \(E_\mathrm{a}/k\) ranges from 8,822 K (761 meV) at \(\mu \) \(_{0} H_{dc}\) = 0 T to 1,100 K (95 meV) at 18 T for \(H_\mathrm{ac}=\)80 A/m (1 Oe). The energies drop very quickly in a non-linear manner as \(\mu \) \(_{0} H_\mathrm{dc}\) increases from 0 to 1 T, and more gradually, in a linear-like manner, as \(\mu \) \(_{0} H_\mathrm{dc}\) increases further to 18 T, suggesting some kind of vortex transition. For ac fields of 400 A/m (5 Oe) and higher, the Arrhenius model starts breaking down, at around \(\mu \) \(_{0} H_{ \mathrm dc}\) = 2 T. As the dc magnetic flux density increases further, this breakdown becomes significant for \(\mu _{0} H_\mathrm{dc}\) = 15 and 18 T at ac fields of 400 A/m and higher. Extensive mapping of the de-pinning, or irreversibility, lines shows broad dependence on the magnitude of the ac field, frequency, in addition to the dc magnetic flux density.


Pnictides AC susceptibilty Magnetic measurements  Bulk superconductors Magnetic flux pinning Flux activation energies  Irreversibility line 



This work at The National High Magnetic Field Laboratory was supported by NSF DMR-1006584 and DMR-1306785, the State of Florida, the U.S. Department of Energy, and by NHMFL which is supported by the National Science Foundation under DMR-1157490.


  1. 1.
    M. Rotter, M. Tegel, D. Johrendt, Phys. Rev. Lett. 101, 107006 (2008)ADSCrossRefGoogle Scholar
  2. 2.
    Z.S. Wang, H.Q. Luo, C. Ren, H.H. Wen, Phys. Rev. B 78, 140501 (R) (2008)ADSCrossRefGoogle Scholar
  3. 3.
    M.M. Altarawneh et al., Phys. Rev. B 78, 220505 (R) (2008)ADSCrossRefGoogle Scholar
  4. 4.
    H. Yang, H.Q. Luo, Z.S. Wang, H.H. Wen, Appl. Phys. Lett. 93, 142506 (2008)ADSCrossRefGoogle Scholar
  5. 5.
    R. Prozorov et al., Phys. Rev. B 82, 180513 (R) (2010)ADSCrossRefGoogle Scholar
  6. 6.
    M. Konczykowski et al., Phys. Rev. B 86, 024515 (2012)ADSCrossRefGoogle Scholar
  7. 7.
    M. Nikolo, R.B. Goldfarb, Phys. Rev. B 39, 6615 (1989)ADSCrossRefGoogle Scholar
  8. 8.
    K.-H. Müller, M. Nikolo, R. Driver, Phys. Rev. B 43, 7976 (1991)ADSCrossRefGoogle Scholar
  9. 9.
    M. Nikolo, W. Kiel, H.M. Duan, A.M. Hermann, Phys. Rev. B 45, 5641 (1992)ADSCrossRefGoogle Scholar
  10. 10.
    P.W. Anderson, Phys. Rev. Lett. 9, 309 (1962)ADSCrossRefGoogle Scholar
  11. 11.
    P.W. Anderson, Y.B. Kim, Rev. Mod. Phys. 36, 39 (1964)ADSCrossRefGoogle Scholar
  12. 12.
    J.D. Weiss, J. Jiang, A.A. Polyanskii, E.E. Hellstrom, Supercond. Sci. Tech. 26, 074003 (2013)ADSCrossRefGoogle Scholar
  13. 13.
    R.B. Goldfarb et al., in Magnetic Susceptibility of Superconductors and Other Spin Systems, ed. by R.A. Hein et al. (Plenum Press, New York, 1991), p. 59Google Scholar
  14. 14.
    M. Nikolo, Am. J. Phys. 63, 57 (1995)ADSCrossRefGoogle Scholar
  15. 15.
    A.P. Malozemoff, T.K. Worthington, Y. Yeshurun, F.H. Holtzberg, P.H. Kes, Phys. Rev. B 38, 7203 (1988)ADSCrossRefGoogle Scholar
  16. 16.
    F. Gomory, S. Takacs, T. Holubar, G. Hilscher, Physica C 235–240, 2753 (1994)CrossRefGoogle Scholar
  17. 17.
    T. Ishida et al., Advances in Superconductivity V, 541 (1993)Google Scholar
  18. 18.
    J.R Clem, Ames Report IS-M 280, “Ac Losses in Type-II Superconductors” (1979)Google Scholar
  19. 19.
    F. Gömöry, S. Takács, T. Holubar, G. Hilscher, in Advances in Cryogenic Engineering, Vol. 42, ed. by L.T. Summers (Plenum Press, New York, 1997), p. 587Google Scholar

Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  • M. Nikolo
    • 1
  • X. Shi
    • 2
  • E. S. Choi
    • 2
  • J. Jiang
    • 3
  • J. D. Weiss
    • 3
  • E. E. Hellstrom
    • 3
  1. 1.Physics DepartmentSaint Louis UniversitySt LouisUSA
  2. 2.National High Magnetic Field LaboratoryFlorida State UniversityTallahasseeUSA
  3. 3.Applied Superconductivity Center, National High Magnetic Field LaboratoryFlorida State UniversityTallahasseeUSA

Personalised recommendations