As-75 NMR of Ba(Fe0.93Co0.07)(2)As-2 in high magnetic field

TitleAs-75 NMR of Ba(Fe0.93Co0.07)(2)As-2 in high magnetic field
Publication TypeJournal Article
Year of Publication2011
AuthorsOh S, Mounce AM, Mukhopadhyay S, Halperin WP, Vorontsov AB, Bud'ko SL, Canfield PC, Furukawa Y, Reyes P, Kuhns PL
Journal TitlePhysical Review B
Date Published06
Type of ArticleArticle
ISBN Number1098-0121
Accession NumberISI:000291149900003
Keywordsdependence, mixed-state, platinum, relaxation, RESONANCE, spin-diffusion, superconductors, yba2cu3o7

The superconducting state of an optimally doped single crystal of Ba(Fe0.93Co0.07)(2)As-2 was investigated by As-75 NMR in high magnetic fields from 6.4 to 28 T. It was found that the Knight shift is least affected by vortex supercurrents in high magnetic fields H > 11 T, revealing slow, possibly higher order than linear, increase with temperature at T less than or similar to 0.5 T-c, with T-c approximate to 23 K. This is consistent with the extended s-wave state with A(1g) symmetry, but the precise details of the gap structure are harder to resolve. Measurements of the NMR spin-spin relaxation time T-2 indicate a strong indirect exchange interaction at all temperatures. Below the superconducting transition temperature, abrupt changes in vortex dynamics lead to an anomalous dip in T-2, consistent with vortex freezing from which we obtain the vortex phase diagram up to H = 28 T.

URL<Go to ISI>://000291149900003
Alternate JournalPhys. Rev. B