Volume 87, Number 2, July 2009
|Number of page(s)||6|
|Section||Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties|
|Published online||18 August 2009|
Anisotropic spin fluctuations and multiple superconducting gaps in hole-doped Ba0.72K0.28Fe2As2: NMR in a single crystal
Department of Physics, Okayama University - Okayama 700-8530, Japan
2 Max Planck Institute - Heisenbergstrasse 1, D-70569 Stuttgart, Germany, EU
3 Institute of Physics, Chinese Academy of Sciences - Beijing 100190, China
Corresponding author: email@example.com
Accepted: 17 July 2009
We report the 75As-NMR study on a single crystal of the hole-doped iron-pnictide superconductor Ba0.72K0.28Fe2As2 (Tc = 31.5 K). We find that the Fe antiferromagnetic spin fluctuations are anisotropic and are weaker compared to underdoped copper-oxides or cobalt-oxide superconductors. The spin lattice relaxation rate decreases below Tc with no coherence peak and shows a stepwise variation at low temperatures, which is indicative of multiple superconducting gaps, as in the electron-doped Pr(La)FeAsOFx. Furthermore, no evidence was obtained for a microscopic coexistence of a long-range magnetic order and superconductivity.
PACS: 74.20.Rp – Pairing symmetry (other than s-wave) / 74.25.Jb – Electronic structure / 74.25.Nf – Response to electromagnetic fields (nuclear magnetic resonance, surface impedance, etc.)
© EPLA, 2009
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