Magnetic impurities in the pnictide superconductor Ba1-xK xFe2As2

Sutirtha Mukhopadhyay, Sangwon Oh, A. M. Mounce, Moohee Lee, W. P. Halperin, N. Ni, S. L. Bud'ko, P. C. Canfield, A. P. Reyes, P. L. Kuhns

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Nuclear magnetic resonance (NMR) measurements have been performed on single crystals of Ba1-xKxFe2As2 (x = 0, 0.45) and CaFe2As2 grown from Sn flux. The Ba-based pnictide crystals contain significant amounts of Sn in their structure, ∼1%, giving rise to magnetic impurity effects evident in the NMR spectrum and in the magnetization. Our experiments show that the large impurity magnetization is broadly distributed on a microscopic scale, generating substantial magnetic field gradients. There is a concomitant 20% reduction in the transition temperature, which is most likely due to magnetic electron scattering. We suggest that the relative robustness of superconductivity (x = 0.45) in the presence of severe magnetic inhomogeneity might be accounted for by strong spatial correlations between impurities, such as clustering on the coherence length scale.

Original languageEnglish (US)
Article number055002
JournalNew Journal of Physics
StatePublished - 2009

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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