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arXiv · 0902.1252

Superconducting fluctuations in the reversible magnetization of the iron-pnictide $Ba_{1-x}K_xFe_2As_2$

S. Salem-Sugui Jr.·L. Ghivelder·A. D. Alvarenga·J. L. Pimentel Fr.·Huiqian Luo·Zhaosheng Wang·Hai-Hu Wen
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Abstract

We report on isofield magnetization curves obtained as a function of temperature in two single crystals of $Ba_{1-x}K_xFe_2As_2$ with superconducting transition temperature $T_c$=28K and 32.7 K. Results obtained for fields above 20 kOe show a well defined rounding effect on the reversible region extending 1-3 K above $T_c(H)$ masking the transition. This rounding appears to be due to three-dimensional critical fluctuations, as the higher field curves obey a well know scaling law for this type of critical fluctuations. We also analysed the asymptotic behavior of $\sqrt M$vs.T curves in the reversible region which probes the shape of the gap near $T_c(H)$. Results of the analysis suggests that phase fluctuations are important in $Ba_{1-x}K_xFe_2As_2$ which is consistent with nodes in the gap.

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S. Salem-Sugui Jr., L. Ghivelder, A. D. Alvarenga, J. L. Pimentel Fr., Huiqian Luo, Zhaosheng Wang, Hai-Hu Wen. 2009-07-29. Superconducting fluctuations in the reversible magnetization of the iron-pnictide $Ba_{1-x}K_xFe_2As_2$. https://doi.org/10.1103/physrevb.80.014518

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