Open AccessUpper critical field and thermally activated flux flow in LaFeAsO1−xFx
Author(s) -
MohammadAli Shahbazi,
Xiaolin Wang,
Chandra Shekhar,
O. N. Srivastava,
Zhiwei Lin,
Jianguo Zhu,
Shi Xue Dou
Publication year - 2011
Publication title -
journal of applied physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.699
H-Index - 319
eISSN - 1089-7550
pISSN - 0021-8979
DOI - 10.1063/1.3566069
Subject(s) - superconductivity , flux pinning , critical field , condensed matter physics , magnetic field , doping , flux (metallurgy) , materials science , critical current , atmospheric temperature range , field (mathematics) , analytical chemistry (journal) , chemistry , physics , thermodynamics , metallurgy , chromatography , quantum mechanics , mathematics , pure mathematics
The magneto-resistance, critical current density, Jc, upper critical field, Hc2, and flux pinning properties of LaFeAsO1−xFx superconductors were investigated systematically by magnetic and magneto-transport measurements in the fields up to 13 T over a temperature range of 5–35 K. It was found that the Hc2 increased with increasing fluorine concentration up to x ≤ 0.15, while with higher fluorine doping, Hc2 decreased. A peak effect in the Jc as a function of field was observed at T < 15 K for both the 5% and 15% fluorine doped samples. The broadening of the superconducting transition in magnetic field can be well understood by the thermally activated flux flow model. The pinning potential, Uo, scales as Uo/kB ∝ B−n with n = 0.13 for B < 1 T and n =− 0.68 for B > 1 T for LaFeAsO0.85F0.15
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