Sutirtha Mukhopadhyay

Magnetic impurities in the pnictide superconductor Ba1?xKxFe2As2

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.

As75 NMR of Ba(Fe0.93Co0.07)2As 2 in high magnetic field

The superconducting state of an optimally doped single crystal of Ba(Fe

Charge-induced vortex lattice instability

_{0.93}

Spin-density wave near the vortex cores in the high-temperature superconductor Bi2Sr2CaCu2O8+y.

Co

Evidence for intrinsic impurities in the high-temperature superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} from {sup 17}O nuclear magnetic resonance.

_{0.07}

Effects of Vortex Charge Explored by NMR Spectroscopy in Bi2Sr2CaCu2O8+delta

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Effects of Vortex Charge Explored by NMR Spectroscopy in Bi

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As

Sr

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was investigated by