Sutirtha Mukhopadhyay et al 2009 New J. Phys. 11 055002 doi:10.1088/1367-2630/11/5/055002
Sutirtha Mukhopadhyay1, Sangwon Oh1, A M Mounce1, Moohee Lee2, W P Halperin1,5, N Ni3, S L Bud'ko3, P C Canfield3, A P Reyes4 and P L Kuhns4
Show affiliationsPart of Iron-Based Superconductors
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.
74.25.Nf Response to electromagnetic fields (nuclear magnetic resonance, surface impedance, etc.)
74.70.Dd Ternary, quaternary and multinary compounds (including Chevrel phases, borocarbides, etc.)
Issue 5 (May 2009)
Received 19 February 2009
Published 5 May 2009
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