Magnetic impurities in the pnictide superconductor Ba1-xKxFe2As2

TitleMagnetic impurities in the pnictide superconductor Ba1-xKxFe2As2
Publication TypeJournal Article
Year of Publication2009
AuthorsMukhopadhyay S, Oh S, Mounce AM, Lee M, Halperin WP, Ni N, Bud'ko SL, Canfield PC, Reyes AP, Kuhns PL
Journal TitleNew Journal of Physics
Date Published05/05
ISBN Number1367-2630
Accession NumberISI:000266234300002
Keywordsalloys, coexistence, nmr, probe

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, similar to 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.

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